[flake8] add default configuration

.flake8

@@ -0,0 +1,28 @@
+[flake8]
+ignore = 
+    # line length < 80
+    E501,
+    # spaces around keywords
+    E251,
+    # lambda expressions
+    E731,
+    # line break before binary operator
+    W503,
+    # blank line at end of file
+    W391,
+    # whitespace around arithmetic operator
+    E226,
+    # ambiguous variable name
+    E741,
+
+per-file-ignores =
+    __init__.py: 
+        # imported but unused
+        F401,
+        # unable to detect undefined names
+        F403,
+
+    # comments should start with space
+    example.local_settings.py: E265,
+
+exclude = .git,.venv,__pycache__

.gitignore

@@ -137,3 +137,5 @@ Cache
 .netrwhist
 /.config/nvim/bundle
 
+# flake8
+!/.flake8