Fix continuation-related PEP8 issues

This changeset resolves 105 PEP8 issues: It addresses the following
whitespace-related PEP8 violations:
- E121 continuation line indentation is not a multiple of four
- E122 continuation line missing indentation or outdented
- E123 closing bracket does not match indentation of opening bracket's line
- E124 closing bracket does not match visual indentation
- E125 continuation line does not distinguish itself from next logical line
- E126 continuation line over-indented for hanging indent
- E127 continuation line over-indented for visual indent
- E128 continuation line under-indented for visual indent

The PEP8 threshold has been lowered to 15.
Do you have any idea if this text is user facing? It looks like it (I will i18n in a separate PR if so)