643aad17fa Enable additional flake8 rules (practicalswift)
f020aca297 Minor Python cleanups to make flake8 pass with the new rules enabled (practicalswift)
Pull request description:
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](https://github.com/bitcoin/bitcoin/pull/12987/files?w=1) 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 .
$
```
Tree-SHA512: fc7d5e752298a50d4248afc620ee2c173135b4ca008e48e02913ac968e5a24a5fd5396926047ec62f1d580d537434ccae01f249bb2f3338fa59dc630bf97ca7a
Signed-off-by: pasta <pasta@dashboost.org>
