Use latest version of poetry since bug has been fixed

Cito · Cito · commit b0fa058bacf3 · 2019-05-06T22:44:49.000+02:00
see python-poetry/poetry#1060
diff --git a/.travis.yml b/.travis.yml
@@ -19,7 +19,7 @@ cache:
     - $TRAVIS_BUILD_DIR/.tox
 
 install:
-  - pip install "poetry==0.12.11"
+  - pip install "poetry>=0.12.15"
   - poetry install
 
 script:
diff --git a/pyproject.toml b/pyproject.toml
@@ -47,6 +47,6 @@ bump2version = "^0.5"
 [tool.black]
 target-version = ['py36', 'py37', 'py38']
 [build-system]
-requires = ["poetry==0.12.11"]
+requires = ["poetry>=0.12.15"]
 build-backend = "poetry.masonry.api"
 
