Noissue - Added flake8 extension accounting for our coding style and some other stuff

flake8-abp/README.md

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+# flake8-abp
+
+A [flake8](https://flake8.readthedocs.io) extension that checks for compliance
+with the [Adblock Plus coding style guide](https://adblockplus.org/coding-style#python)
+and some bad practices which flake8 doesn't handle by default.
+
+
+## Installation
+
+Run `python setup.py install`.
+
+
+## Usage
+
+Just run `flake8` (you have to install it seperately) on your source files.
+After installation the `flake8-abp` extension is active by default.
+
+
+## Warnings
+
+### Readability and consistency
+
+* `A101`: Loop over a tuple or set literal; use lists for data that have order
+* `A102`: Membership check on a tuple or list literal; use a set here
+* `A103`: Yoda condition
+* `A104`: `map()` or `filter()` called with lambda function
+* `A105`: Type called with literal or comprehension where a
+          literal/comprehension of that type can be used directly
+* `A106`: Use augment assignment
+* `A107`: `%` operator used for string formatting; this mechanism
+          has been superseded by the string's `format()` method
+* `A108`: `+` operator to concatenate more than two strings
+* `A109`: Use triple double quotes for docstrings as recommended in PEP-257
+* `A110`: Write single-line string literals as represented by `repr()`
+* `A111`: Redundant parantheses around if or while condition
+
+
+### Redundancy and complexity
+
+* `A201`: Redundant or superfluos `global` or `nonlocal` declaration
+* `A202`: Dead code after block is left
+* `A303`: Unused expression
+* `A204`: Redundant or superfluos pass statement 
+* `A205`: Superfluos empty block 
+* `A206`: `else` statement after block is left 

[Vasily Kuznetsov, 2016/05/09 15:45:13]

Maybe "Extraneous else" (in reference to
https://www.youtube.com/watch?v=JVVMMULwR4s&t=4m53s) or even the full title of
the talk (Eschew the extraneous else).

[Sebastian Noack, 2016/05/09 16:49:12]

Hehe, that talk is awesome. I saw it last year at EuroPython. Done.

[Vasily Kuznetsov, 2016/05/09 17:37:33]

Yeah, me too.

+* `A207`: Duplicate key in dict or set
+
+
+### Error-prone practices
+
+* `A301`: Discouraged APIs
+* `A302`: Redefinition of built-in name
+* `A303`: Non-default source file encoding