Enabled checks for E226, E251, E265

Thoas checks are also enabled in Horizon and should be enabled here as well.

* E226 missing whitespace around arithmetic operator
* E251 unexpected spaces around keyword / parameter equals
* E265 block comment should start with '# '

Change-Id: Ib44fd1b327c23752acfc5b98cd468881b781c816
Merge "Enabled checks for E226, E251, E265"