travis.yml: Fix build issues

This adds changes to fix the dependency
issues due to coverage and pytest along
with jdk version fix and pip version.

Closes #6133

.travis.yml

@@ -40,7 +40,7 @@ jobs:
   include:
     - stage: sentinel
       # All other jobs will be cancelled if the sentinel job fails
-      python: 3.6
+      python: 3.6.9
 
     - stage: test
       # The sentinel job isnt active on master pushes, so the
@@ -77,7 +77,7 @@ env:
     - PATH="$PATH:$TRAVIS_BUILD_DIR/node_modules/.bin"
     - BEARS_ZIP_URL=https://codeload.github.com/coala/coala-bears/zip
     - GRAVIS="https://raw.githubusercontent.com/DanySK/Gravis-CI/master/"
-    - JDK="adopt@1.8.0-212"
+    - JDK="adopt@1.8.0-275"
 
 cache:
   pip: true
@@ -107,7 +107,7 @@ before_install:
   - pip uninstall setuptools --yes || true
   - pip uninstall setuptools --yes || true
   - pip uninstall pipenv --yes || true
-  - pip install pip==9.0.1 setuptools==21.2.2
+  - pip install pip==9.0.3 setuptools==21.2.2
   - python .misc/check_setuptools.py
 
   # https://github.com/coala/coala/issues/3183

setup.cfg

@@ -21,7 +21,7 @@ addopts =
   --color=yes
   --doctest-glob=*.rst
   --doctest-modules
-  --doctest-ignore-import-error
+  --doctest-ignore-import-errors
   --error-for-skips
   --cov
   --instafail

test-requirements.txt

@@ -7,14 +7,14 @@ argcomplete~=1.8
 # coverage 4.4.2 broke compatibility with coverage-config-reload-plugin
 # and thus broke https://github.com/jayvdb/coverage_env_plugin .
 # See https://github.com/jayvdb/coverage_config_reload_plugin/issues/1
-coverage==4.4.1
+coverage>=5.2.1
 coverage-env-plugin~=0.1
 coverage-config-reload-plugin~=0.2
 codecov~=2.0.5
 freezegun~=0.3.9
 moban~=0.5.0 ; python_version > '3.0'
 pytest~=3.6.4
-pytest-cov~=2.4
+pytest-cov>=2.4,<2.6
 pytest-env~=0.6.0
 pytest-error-for-skips~=1.0
 pytest-instafail~=0.3.0