PEP: be explicit about what errors are ignored.

Change-Id: I362ba16c8a7b645c9befa7fcd4b0942773b0dbce
Fix PEP H402 "one line docstring needs punctuation."

Change-Id: Id0aa43187f6d5e62308f4b329bc9458a512d808d
Fix PEP H301 (one import per line)

Change-Id: I7b0c991c869c903e60123ad5bdf876b06d83e3e9