[Travis] add linting via pyflakes

See #889, See #770

.github/PULL_REQUEST_TEMPLATE.md

@@ -11,7 +11,12 @@
 *
 ### Checklist
 - [ ] The code change is tested and works locally.
-- [ ] Tests pass. Your PR cannot be merged unless tests pass
+- [ ] Tests pass. Your PR cannot be merged unless tests pass.
+- [ ] The code passes linting via
+  [black](https://black.readthedocs.io/en/stable/) (consistent code styling) --
+  `black --check . --verbose --diff`
+- [ ] The code passes linting via [pyflakes](https://launchpad.net/pyflakes)
+  (logically errors and unused imports) -- `pyflakes .`
 - [ ] There is no commented out code in this PR.
 - [ ] Have you followed the guidelines in our Contributing document?
 - [ ] Have you checked to ensure there aren't other open [Pull Requests](../pulls) for the same update/change?

.gitignore

@@ -42,6 +42,7 @@ obj
 # virtaulenv
 env/
 env*/
+venv*/
 
 # PyCharm Project files
 .idea/

.travis.yml

@@ -62,11 +62,17 @@ jobs:
     - python: nightly
 
   include:
+    # Linting
     - name: Lint, via Black
       python: 3.8
       script:
         - black --version
         - black --check . --verbose --diff
+    - name: Lint, via PyFlakes
+      python: 3.8
+      script:
+        - pyflakes --version
+        - pyflakes .
 
     # Python 3.6 Tests
     - name: Python 3.6 on Linux

poetry.lock

@@ -522,7 +522,7 @@ docs = ["sphinx", "jaraco.packaging (>=3.2)", "rst.linker (>=1.9)"]
 testing = ["jaraco.itertools", "func-timeout"]
 
 [metadata]
-content-hash = "17cf8d4cf5a772217160daf312f590901dea4a3f5545d003035f3fb713a70f07"
+content-hash = "f49f70401f1b2e1d9cc5f7766a96288b260fddb37a21b4789feaac0d34838abf"
 python-versions = ">=3.6.0, <3.9.0"
 
 [metadata.files]

pyproject.toml

@@ -35,6 +35,7 @@ behave = "^1.2"
 mkdocs = "^1.0"
 flake8 = "^3.7"
 black = {version = "^19.10b0",allow-prereleases = true}
+pyflakes = "^2.1.0"
 
 [tool.poetry.scripts]
 jrnl = 'jrnl.cli:run'