Add linting (atlassian-api#612)

* Keep dev deps DRY

* Use tox-travis

* Add flake8/pylint/black/mypy/bandit/doc8 to tox

* Fix flake8/pep8 errors

* Conform with pylint C0103

* Fix pylint errors

* Add missing return statements

* Skip integration tests if credentials not provided

* Fix doc8 errors

* Apply black formatter

* Remove Python 3.3 from CI matrix

It's not available on Xenial 16.04 anyway: https://docs.travis-ci.com/user/languages/python/

* Update CI Python version matrix

.travis.yml

@@ -1,20 +1,20 @@
 language: python
 python:
-    - "2.7"
-    - "3.3"
-    - "3.4"
-    - "3.5"
-    - "3.6"
-    - "3.7"
-    - "3.8"
-    - "3.9-dev"
+  - "2.7"
+  - "3.4"
+  - "3.5"
+  - "3.6"
+  - "3.7"
+  - "3.8"
+  - "3.9"
+  - "3.10-dev"
 
 matrix:
   allow_failures:
-    - python: "3.3"
+    - python: "3.10-dev"
 
-install: pip install tox
-before_script: 
-    - .travis/bump_version ./ minor > atlassian/VERSION
+install: pip install tox-travis
+before_script:
+  - .travis/bump_version ./ minor > atlassian/VERSION
 script:
-    - tox
+  - tox

atlassian/__init__.py

@@ -10,14 +10,14 @@
 from .xray import Xray
 
 __all__ = [
-    'Confluence',
-    'Jira',
-    'Bitbucket',
-    'Portfolio',
-    'Bamboo',
-    'Stash',
-    'Crowd',
-    'ServiceDesk',
-    'MarketPlace',
-    'Xray'
+    "Confluence",
+    "Jira",
+    "Bitbucket",
+    "Portfolio",
+    "Bamboo",
+    "Stash",
+    "Crowd",
+    "ServiceDesk",
+    "MarketPlace",
+    "Xray",
 ]