diff --git a/.gitignore b/.gitignore
index 0e60aab..e885032 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@
 /result*
 /examples/generated*
 /deploy_rsa
+*~
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index ffddb3d..65d0db8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,7 +28,7 @@ before_install:
   - export SSL_CERT_FILE=$PWD/result-cacert/etc/ssl/certs/ca-bundle.crt
   - sudo mkdir -p /etc/ssl/certs/ && sudo rm -f /etc/ssl/certs/ca-certificates.crt && sudo ln -s $PWD/result-cacert/etc/ssl/certs/ca-bundle.crt /etc/ssl/certs/ca-certificates.crt
   - echo 'binary-caches = https://cache.nixos.org/ https://travis.garbas.si/pypi2nix/' | sudo tee -a /etc/nix/nix.conf > /dev/null
-  - if [ "$TRAVIS_PULL_REQUEST" != "true" -a "$TRAVIS_BRANCH" = "master" ]; then
+  - if [ "$TRAVIS_PULL_REQUEST" = "false" -a "$TRAVIS_BRANCH" = "master" ]; then
       openssl aes-256-cbc -K $encrypted_0cfcc1944c73_key -iv $encrypted_0cfcc1944c73_iv -in deploy_rsa.enc -out deploy_rsa -d;
       eval "$(ssh-agent -s)";
       chmod 600 $TRAVIS_BUILD_DIR/deploy_rsa;
@@ -36,12 +36,12 @@ before_install:
     fi
 script:
   - cd examples && make $EXAMPLE && cd ..
-  - if [ "$TRAVIS_PULL_REQUEST" != "true" -a "$TRAVIS_BRANCH" = "master" ]; then
+  - if [ "$TRAVIS_PULL_REQUEST" = "false" -a "$TRAVIS_BRANCH" = "master" ]; then
       mkdir nars/;
       nix-push --dest "$PWD/nars/" --force ./examples/$EXAMPLE;
     fi
 after_success:
-  - if [ "$TRAVIS_PULL_REQUEST" != "true" -a "$TRAVIS_BRANCH" = "master" ]; then
+  - if [ "$TRAVIS_PULL_REQUEST" = "false" -a "$TRAVIS_BRANCH" = "master" ]; then
       rsync -avh --ignore-existing $TRAVIS_BUILD_DIR/nars/ travis@garbas.si:/var/travis/pypi2nix/;
     fi
 
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..e2d334e
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,5 @@
+flakes:
+	nix-shell '<nixpkgs>' -p python3Packages.flake8 --command \
+		'flake8 src/ --ignore E501'
+
+.PHONY: flakes
diff --git a/default.nix b/default.nix
index cb5c5cc..3c92ed6 100644
--- a/default.nix
+++ b/default.nix
@@ -1,4 +1,5 @@
-{ stdenv, fetchurl, python, zip, makeWrapper, nix, nix-prefetch-scripts
+{ stdenv, fetchurl, zip, makeWrapper, nix, nix-prefetch-scripts
+, pythonPackages
 , src ? { outPath = ./.; name = "pypi2nix"; }
 }:
 
@@ -23,7 +24,11 @@ in stdenv.mkDerivation rec {
     click
     requests
   ];
-  buildInputs = [ python zip makeWrapper nix.out nix-prefetch-scripts ];
+  buildInputs = [
+    pythonPackages.python pythonPackages.flake8
+    zip makeWrapper nix.out nix-prefetch-scripts
+  ];
+  doCheck = true;
   sourceRoot = ".";
 
   postUnpack = ''
@@ -50,7 +55,7 @@ in stdenv.mkDerivation rec {
   commonPhase = ''
     mkdir -p $out/bin
 
-    echo "#!${python.interpreter}" >  $out/bin/pypi2nix
+    echo "#!${pythonPackages.python.interpreter}" >  $out/bin/pypi2nix
     echo "import pypi2nix.cli" >> $out/bin/pypi2nix
     echo "pypi2nix.cli.main()" >> $out/bin/pypi2nix
 
@@ -59,6 +64,10 @@ in stdenv.mkDerivation rec {
     export PYTHONPATH=$out/pkgs:$PYTHONPATH
   '';
 
+  checkPhase = ''
+    flake8 ${src}/src
+  '';
+
   installPhase = commonPhase + ''
     wrapProgram $out/bin/pypi2nix --prefix PYTHONPATH : "$PYTHONPATH"
   '';
diff --git a/release.nix b/release.nix
index e94bf52..7f46076 100644
--- a/release.nix
+++ b/release.nix
@@ -10,8 +10,8 @@ let
     if builtins.elem system supportedSystems
       then import ./default.nix {
         inherit (pkgs) stdenv fetchurl zip makeWrapper nix nix-prefetch-scripts;
-        python = pkgs.python35;
         src = pypi2nix;
+        pythonPackages = pkgs.python3Packages;
       }
       else abort "Unsupported system type: ${system}";
 
diff --git a/shell.nix b/shell.nix
index 908ca09..1cfc587 100644
--- a/shell.nix
+++ b/shell.nix
@@ -5,8 +5,8 @@
 
 let
   pkgs = import nixpkgs {};
-  python = (builtins.getAttr "python${pythonVersion}Packages" pkgs).python;
+  pythonPackages = builtins.getAttr "python${pythonVersion}Packages" pkgs;
 in import ./default.nix {
-  inherit src python;
+  inherit src pythonPackages;
   inherit (pkgs) stdenv fetchurl zip makeWrapper nix nix-prefetch-scripts;
 }
diff --git a/src/pypi2nix/cli.py b/src/pypi2nix/cli.py
index 66644d2..a2f932c 100644
--- a/src/pypi2nix/cli.py
+++ b/src/pypi2nix/cli.py
@@ -195,12 +195,13 @@ def handle_requirements_file(project_dir, requirements_file):
             with open(new_requirements_file, "w+") as f2:
                 for requirements_line in f1.readlines():
                     if requirements_line.startswith("-e git+") or \
-                           requirements_line.startswith("-e hg+"):
+                       requirements_line.startswith("-e hg+"):
                         pass
                     elif requirements_line.startswith("-e"):
                         requirements_line = requirements_line.strip()[3:]
                         try:
-                            tmp_path, egg = requirements_line.strip().split('#')
+                            tmp_path, egg = requirements_line.strip() \
+                                                             .split('#')
                             tmp_name = egg.split('egg=')[1]
                             _tmp = tmp_path.split('[')
                             if len(_tmp) > 1:
@@ -229,7 +230,7 @@ def handle_requirements_file(project_dir, requirements_file):
                     elif requirements_line.startswith("-r ./"):
                         requirements_file2 = os.path.abspath(os.path.join(
                             os.path.dirname(requirements_file),
-                                            requirements_line.strip()[3:]
+                            requirements_line.strip()[3:]
                         ))
                         new_requirements_file2 = handle_requirements_file(
                             project_dir, requirements_file2)
@@ -251,7 +252,8 @@ def handle_requirements_file(project_dir, requirements_file):
     click.echo('')
 
     if buildout:
-        click.echo('Stage0: Generating requirements.txt from buildout configuration ...')
+        click.echo('Stage0: Generating requirements.txt from buildout '
+                   'configuration ...')
         buildout_requirements = pypi2nix.stage0.main(
             verbose=verbose,
             buildout_file=buildout,
@@ -319,7 +321,6 @@ def handle_requirements_file(project_dir, requirements_file):
         current_dir=current_dir,
     )
 
-
     click.echo('')
     click.echo('Nix expressions generated successfully.')
     click.echo('')
diff --git a/src/pypi2nix/stage0.py b/src/pypi2nix/stage0.py
index 041a654..10fe403 100644
--- a/src/pypi2nix/stage0.py
+++ b/src/pypi2nix/stage0.py
@@ -40,5 +40,7 @@ def main(verbose,
         raise click.ClickException(
             u'While trying to run the command something went wrong.')
 
-
-    return buildout_file and os.path.join(project_dir, 'buildout_requirements.txt') or None
+    return buildout_file and \
+        os.path.join(project_dir,
+                     'buildout_requirements.txt') \
+        or None
diff --git a/src/pypi2nix/stage1.py b/src/pypi2nix/stage1.py
index 386302c..575ef40 100644
--- a/src/pypi2nix/stage1.py
+++ b/src/pypi2nix/stage1.py
@@ -71,7 +71,7 @@ def main(verbose,
 
     returncode, output = pypi2nix.utils.cmd(command, verbose != 0)
     if returncode != 0 or \
-           output.endswith('ERROR: Failed to build one or more wheels'):
+       output.endswith('ERROR: Failed to build one or more wheels'):
         if verbose == 0:
             click.echo(output)
 
@@ -80,9 +80,10 @@ def main(verbose,
         # trying to recognize the problem and provide more meanigful error
         # message
         no_matching_dist = "No matching distribution found for "
-        no_pg_config = "Error: pg_config executable not found."
         if no_matching_dist in output:
-            dist_name = output[output.find(no_matching_dist) + len(no_matching_dist):]
+            dist_name = output[
+                output.find(no_matching_dist) + len(no_matching_dist):
+            ]
             dist_name = dist_name[:dist_name.find(' (from')]
             message = (
                 "Most likely `%s` package does not have source (zip/tar.bz) "
@@ -94,7 +95,8 @@ def main(verbose,
             if click.confirm('Do you want to report above issue (a browser '
                              'will open with prefilled details of issue)?'):
                 title = "Error when running pypi2nix command"
-                body = "# Description\n\n<detailed description of error here>\n\n"
+                body = "# Description\n\n<detailed description of error "
+                "here>\n\n"
                 body += "# Traceback \n\n```bash\n"
                 body += "% pypi2nix --version\n"
                 with open(os.path.join(HERE, 'VERSION')) as f:
diff --git a/src/pypi2nix/stage2.py b/src/pypi2nix/stage2.py
index 4e4930f..4d583d9 100644
--- a/src/pypi2nix/stage2.py
+++ b/src/pypi2nix/stage2.py
@@ -1,4 +1,5 @@
 """Parse metadata from .dist-info directories in a wheelhouse."""
+# flake8: noqa: E501
 
 import click
 import hashlib
@@ -56,7 +57,6 @@ def extract_deps(metadata):
 
     return list(set(deps))
 
-
 all_classifiers = {
     'License :: Aladdin Free Public License (AFPL)': None,
     'License :: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication': None,
@@ -226,7 +226,7 @@ def find_release(wheel_cache_dir, wheel, wheel_data):
     if not _releases:
         for _version, _releases_tmp in wheel_data['releases'].items():
             if pkg_resources.parse_version(wheel['version']) == \
-                   pkg_resources.parse_version(_version):
+               pkg_resources.parse_version(_version):
                 _release_version = _version
                 _releases = _releases_tmp
                 break
@@ -294,9 +294,8 @@ def process_wheel(wheel_cache_dir, wheel, sources, verbose, index=INDEX_URL,
         release['hash_type'] = 'sha256'
 
         repo_type = sources[wheel['name']]['type']
-        if repo_type is None and \
-               (release['url'].startswith('http://') or \
-                release['url'].startswith('https://')):
+        if repo_type is None and (release['url'].startswith('http://') or
+                                  release['url'].startswith('https://')):
 
             release['fetch_type'] = 'fetchurl'
 
@@ -388,14 +387,12 @@ def process_wheel(wheel_cache_dir, wheel, sources, verbose, index=INDEX_URL,
         else:
             raise click.ClickException('Source type `{}` not implemented'.format(repo_type))
 
-
     else:
         url = "{}/{}/json".format(index, wheel['name'])
         r = requests.get(url, timeout=None)
         r.raise_for_status()  # TODO: handle this nicer
         wheel_data = r.json()
 
-
         if not wheel_data.get('releases'):
             raise click.ClickException(
                 "Unable to find releases for packge {name}".format(**wheel))
@@ -427,8 +424,10 @@ def main(verbose, wheels, requirements_files, wheel_cache_dir, index=INDEX_URL,
                         "Source for path `%s` does not exists." % line
                     )
 
-                elif line.startswith('http://') or line.startswith('https://') or \
-                     line.startswith('git+') or line.startswith('hg+'):
+                elif (line.startswith('http://') or
+                      line.startswith('https://') or
+                      line.startswith('git+') or
+                      line.startswith('hg+')):
                     try:
                         url, egg = line.split('#')
                         name = egg.split('egg=')[1]
diff --git a/src/pypi2nix/stage3.py b/src/pypi2nix/stage3.py
index 54f31dd..a731c92 100644
--- a/src/pypi2nix/stage3.py
+++ b/src/pypi2nix/stage3.py
@@ -18,7 +18,8 @@
   inherit (pkgs) makeWrapper;
   inherit (pkgs.stdenv.lib) fix' extends inNixShell;
 
-  pythonPackages = import "${toString pkgs.path}/pkgs/top-level/python-packages.nix" {
+  pythonPackages =
+  import "${toString pkgs.path}/pkgs/top-level/python-packages.nix" {
     inherit pkgs;
     inherit (pkgs) stdenv;
     python = pkgs.%(python_version)s;
@@ -35,8 +36,10 @@
         buildInputs = [ makeWrapper ] ++ (builtins.attrValues pkgs);
         buildCommand = ''
           mkdir -p $out/bin
-          ln -s ${pythonPackages.python.interpreter} $out/bin/${pythonPackages.python.executable}
-          for dep in ${builtins.concatStringsSep " " (builtins.attrValues pkgs)}; do
+          ln -s ${pythonPackages.python.interpreter} \
+              $out/bin/${pythonPackages.python.executable}
+          for dep in ${builtins.concatStringsSep " " \
+              (builtins.attrValues pkgs)}; do
             if [ -d "$dep/bin" ]; then
               for prog in "$dep/bin/"*; do
                 if [ -f $prog ]; then
@@ -67,7 +70,8 @@
 
   python = withPackages {};
 
-  generated = import %(generated_file)s { inherit pkgs python commonBuildInputs commonDoCheck; };
+  generated = import %(generated_file)s
+      { inherit pkgs python commonBuildInputs commonDoCheck; };
   overrides = import %(overrides_file)s { inherit pkgs python; };
 
 in python.withPackages (fix' (extends overrides generated))
@@ -122,10 +126,18 @@ def main(packages_metadata,
     '''Create Nix expressions.
     '''
 
-    default_file = os.path.join(current_dir, '{}.nix'.format(requirements_name))
-    generated_file = os.path.join(current_dir, '{}_generated.nix'.format(requirements_name))
-    overrides_file = os.path.join(current_dir, '{}_override.nix'.format(requirements_name))
-    frozen_file = os.path.join(current_dir, '{}_frozen.txt'.format(requirements_name))
+    default_file = os.path.join(
+        current_dir, '{}.nix'.format(requirements_name)
+    )
+    generated_file = os.path.join(
+        current_dir, '{}_generated.nix'.format(requirements_name)
+    )
+    overrides_file = os.path.join(
+        current_dir, '{}_override.nix'.format(requirements_name)
+    )
+    frozen_file = os.path.join(
+        current_dir, '{}_frozen.txt'.format(requirements_name)
+    )
 
     version_file = os.path.join(os.path.dirname(__file__), 'VERSION')
     with open(version_file) as f:
@@ -137,36 +149,41 @@ def main(packages_metadata,
     for item in sorted(packages_metadata, key=lambda x: x['name']):
         propagatedBuildInputs = '[ ]'
         if item.get('deps'):
-            deps = [x for x in item['deps'] if x.lower() in metadata_by_name.keys()]
+            deps = [x for x in item['deps']
+                    if x.lower() in metadata_by_name.keys()]
             if deps:
                 propagatedBuildInputs = "[\n%s\n    ]" % (
                     '\n'.join(sorted(
-                        ['      self."%s"' % (metadata_by_name[x.lower()]['name'])
-                        for x in deps if x not in [item['name']]
-                    ])))
+                        ['      self."%s"' %
+                         (metadata_by_name[x.lower()]['name'])
+                         for x in deps if x not in [item['name']]]
+                    )))
         fetch_type = item.get('fetch_type', None)
         if fetch_type == 'path':
-            fetch_expression =  './' + os.path.relpath(item['url'], current_dir)
+            fetch_expression = './' + os.path.relpath(item['url'], current_dir)
         elif fetch_type == 'fetchgit':
-            fetch_expression = 'pkgs.fetchgit { url = "%(url)s"; %(hash_type)s = "%(hash_value)s"; rev = "%(rev)s"; }' % dict(
-                url=item['url'],
-                hash_type=item['hash_type'],
-                hash_value=item['hash_value'],
-                rev=item['rev']
-            )
+            fetch_expression = 'pkgs.fetchgit { url = "%(url)s"; '\
+                '%(hash_type)s = "%(hash_value)s"; rev = "%(rev)s"; }' % dict(
+                    url=item['url'],
+                    hash_type=item['hash_type'],
+                    hash_value=item['hash_value'],
+                    rev=item['rev']
+                )
         elif fetch_type == 'fetchhg':
-            fetch_expression = 'pkgs.fetchhg { url = "%(url)s"; %(hash_type)s = "%(hash_value)s"; rev = "%(rev)s"; }' % dict(
-                url=item['url'],
-                hash_type=item['hash_type'],
-                hash_value=item['hash_value'],
-                rev=item['rev']
-            )
+            fetch_expression = 'pkgs.fetchhg { url = "%(url)s"; '\
+                '%(hash_type)s = "%(hash_value)s"; rev = "%(rev)s"; }' % dict(
+                    url=item['url'],
+                    hash_type=item['hash_type'],
+                    hash_value=item['hash_value'],
+                    rev=item['rev']
+                )
         else:
-            fetch_expression='pkgs.fetchurl { url = "%(url)s"; %(hash_type)s = "%(hash_value)s"; }' % dict(
-                url=item['url'],
-                hash_type=item['hash_type'],
-                hash_value=item['hash_value'],
-            )
+            fetch_expression = 'pkgs.fetchurl { url = "%(url)s"; '\
+                '%(hash_type)s = "%(hash_value)s"; }' % dict(
+                    url=item['url'],
+                    hash_type=item['hash_type'],
+                    hash_value=item['hash_value'],
+                )
 
         generated_packages_metadata.append(dict(
             name=item.get("name", ""),
@@ -188,9 +205,11 @@ def main(packages_metadata,
         version=version,
         command_arguments=' '.join(sys.argv[1:]),
         python_version=python_version,
-        extra_build_inputs=extra_build_inputs
-            and "with pkgs; [ %s ]" % (' '.join(extra_build_inputs))
-            or "[]",
+        extra_build_inputs=(
+            extra_build_inputs and
+            "with pkgs; [ %s ]" % (' '.join(extra_build_inputs)) or
+            "[]"
+        ),
         generated_file='.' + generated_file[len(current_dir):],
         overrides_file='.' + overrides_file[len(current_dir):],
         enable_tests=str(enable_tests).lower(),
diff --git a/src/pypi2nix/utils.py b/src/pypi2nix/utils.py
index 78fdb27..133ff93 100644
--- a/src/pypi2nix/utils.py
+++ b/src/pypi2nix/utils.py
@@ -29,9 +29,10 @@ def pretty_option(option):
         return ''
     else:
         return ' [value: {}]'.format(
-            type(option) in [list, tuple]
-            and ' '.join(option)
-            or option)
+            type(option) in [list, tuple] and
+            ' '.join(option) or
+            option)
+
 
 def safe(string):
     return string.replace('"', '\\"')
@@ -49,7 +50,7 @@ def cmd(command, verbose=False):
         command,
         stdout=subprocess.PIPE,
         stderr=subprocess.STDOUT,
-        )
+    )
 
     out = []
     while True: