Move dev dependency specification to environment.yml

Delete the requirements-dev.txt file, and update the ci_test.yml to install GMT dependencies directly from environment.yml.

Author: weiji14

.github/workflows/ci_tests.yaml

@@ -59,15 +59,7 @@ jobs:
       # Install GMT and other required dependencies from conda-forge
       - name: Install GMT and required dependencies
         shell: bash -l {0}
-        run: |
-          requirements_file=full-conda-requirements.txt
-          cat requirements.txt requirements-dev.txt > $requirements_file
-          cat << EOF >> $requirements_file
-          gmt=6.1.1
-          make
-          codecov
-          EOF
-          conda install --yes --file $requirements_file
+        run: conda install --yes --file environment.yml
 
       # Show installed pkg information for postmortem diagnostic
       - name: List installed packages

MAINTENANCE.md

@@ -42,7 +42,7 @@ The main advantages of this are:
 
 We use GitHub Actions continuous integration (CI) services to
 build and test the project on Linux, macOS and Windows.
-They rely on the `requirements.txt` file to install required dependencies using
+They rely on the `environment.yml` file to install required dependencies using
 conda and the `Makefile` to run the tests and checks.
 
 ### GitHub Actions

environment.yml

@@ -3,7 +3,6 @@ channels:
     - conda-forge
     - defaults
 dependencies:
-    - python=3.8
     - pip
     - gmt=6.1.1
     - numpy
@@ -13,12 +12,14 @@ dependencies:
     - packaging
     - black
     - blackdoc
+    - codecov
     - coverage[toml]
     - docformatter
     - flake8
     - ipython
     - isort>=5
     - jupyter
+    - make
     - matplotlib
     - nbsphinx
     - pylint