Fix the following new errors:
* E305 expected 2 blank lines after class or function definition, found 1
* E126 continuation line over-indented for hanging indent
max_line_length is set to 80 as the default value in pycodestyle is 79
but horizon uses 80 as max_line_length.
Ignore W504 and F405 by configurations.
Reasons of disabling them are explained as comments in tox.ini.
Change-Id: Iee8bcd60c30883fc8c74f08cf20af853cbb5e271