tests/tools: Enable additional Python flake8 rules for automatic linting via Travis #12987

Enabled rules:

* E242: tab after ','
* E266: too many leading '#' for block comment
* E401: multiple imports on one line
* E402: module level import not at top of file
* E701: multiple statements on one line (colon)
* E901: SyntaxError: invalid syntax
* E902: TokenError: EOF in multi-line string
* F821: undefined name 'Foo'
* W293: blank line contains whitespace
* W606: 'async' and 'await' are reserved keywords starting with Python 3.7

Note to reviewers:

• In general we don't allow whitespace cleanups to existing code, but in order to allow for enabling Travis checking for these rules a few smaller whitespace cleanups had to made as part of this PR.
• Use this ?w=1 link to show a diff without whitespace changes.

Before this commit:

$ flake8 -qq --statistics --ignore=B,C,E,F,I,N,W --select=E112,E113,E115,E116,E125,E131,E133,E223,E224,E242,E266,E271,E272,E273,E274,E275,E304,E306,E401,E402,E502,E701,E702,E703,E714,E721,E741,E742,E743,F401,E901,E902,F402,F404,F406,F407,F601,F602,F621,F622,F631,F701,F702,F703,F704,F705,F706,F707,F811,F812,F821,F822,F823,F831,F841,W292,W293,W504,W601,W602,W603,W604,W605,W606 .
5     E266 too many leading '#' for block comment
4     E401 multiple imports on one line
6     E402 module level import not at top of file
5     E701 multiple statements on one line (colon)
1     F812 list comprehension redefines 'n' from line 159
4     F821 undefined name 'ConnectionRefusedError'
28    W293 blank line contains whitespace

After this commit:

$ flake8 -qq --statistics --ignore=B,C,E,F,I,N,W --select=E112,E113,E115,E116,E125,E131,E133,E223,E224,E242,E266,E271,E272,E273,E274,E275,E304,E306,E401,E402,E502,E701,E702,E703,E714,E721,E741,E742,E743,F401,E901,E902,F402,F404,F406,F407,F601,F602,F621,F622,F631,F701,F702,F703,F704,F705,F706,F707,F811,F812,F821,F822,F823,F831,F841,W292,W293,W504,W601,W602,W603,W604,W605,W606 .
$

I am fine with removing the trailing white space, since that is now enforced for a couple of months. Though, I don't like to enforce strict rules on leading white space or statements that are otherwise identical.

@MarcoFalke Thanks for reviewing. Good feedback! Now updated. Please re-review :-)

Other than W293, I'd drop all those that seem to enforce white space in a specific way. I'd rather avoid being extra strict on everyone and prescribe exactly how to use whitespace "properly".

@MarcoFalke Thanks for clarifying!

Of the whitespace related rule changes these can be divided into 1.) indentation related and 2.) related to whitespace around operators.

Indentation related:

1     E121 continuation line under-indented for hanging indent
1     E123 closing bracket does not match indentation of opening bracket's line
1     E124 closing bracket does not match visual indentation
2     E126 continuation line over-indented for hanging indent
1     E129 visually indented line with same indent as next logical line

Related to whitespace around operators:

7     E222 multiple spaces after operator
4     E228 missing whitespace around modulo operator

Do you want to get rid of all rules above, or only the indentation related? :-)

Personally, I'd prefer to get rid of all of them for now. (If you or someone else feels strongly about them, they can put them in a separate pull request)

@MarcoFalke Updated! Please re-review :-)

utACK 21cc7ddc0406ee3c76623e7f23dbbcd2d0b6f241

@MarcoFalke Updated! Please re-re-review :-)

re-utACK bf0d779

utACK 96455458ab3f7183141eb64d6e7c3abe11c7a355. Seems like useful cleanup.

Please fixup the travis failure.

@MarcoFalke Thanks for the ping! Fixed!

Please re-review :-)

utACK 643aad17faf104510ba123b596676256f26549c2