Enables H306 pep8 rules

Updates tox.ini to reduce ignored rules.

Updates code for H306 violation.

Change-Id: I9beea02510a1122afb55ad3df3b37f770fe05134
Allow graceful shutdown on Ctrl+C

Currently it prints a stacktrace and exits. This patch makes it print
a message and exit gracefully.

Closes-Bug: #1256732

Change-Id: I59ae8d09be43cd3e56dbe9bed4f6f328377dcc13
Merge "Allow graceful shutdown on Ctrl+C"
Enables H403 pep8 rules

Updates tox.ini to reduce ignored rules.

Updates code for H403 violation.

Change-Id: Iee7b34a27c62ce8cb0f26166b3c16e3386e2fecd
Merge "Enables H306 pep8 rules"
Merge "Enables H403 pep8 rules"