Merge remote-tracking branch 'origin/master' into fix_deprecated_import

.travis.yml

@@ -6,19 +6,22 @@ python:
       - "3.5-dev"
       - "3.6"
       - "3.6-dev"
-      - "nightly" # currently points to 3.7-dev
+      - "3.7"
+      - "3.8"
+      - "nightly"
 
 matrix:
   allow_failures:
     - python: "nightly"
 
 install:
-    - "pip install --editable .[dev]"
-    - "pip install python-coveralls"
+    - pip install --editable .[dev]
+    - if [[ $TRAVIS_PYTHON_VERSION < 3.5 ]] ; then pip install 'pytest==3.8.2' ; elif [[ $TRAVIS_PYTHON_VERSION < 3.6 ]] ; then pip install 'pytest>=5.4.3' ; fi
+    - pip install coveralls
 script:
-    - "pytest -v  --cov-report= --cov=quaternions tests/"
+    - pytest -v  --cov-report= --cov=quaternions tests/
 after_script:
-    - "flake8 quaternions"
+    - flake8 quaternions
 
 # report coverage to coveralls.io
 after_success: