Fix KeyError while generating a WSGI response

The KeyError exception raised while generating a WSGI response based on
the 413 exception. Because there may be no "Retry-After" attribute in the
exception headers.

Change-Id: I89eb1878acc2195775be17fbcba8088f2e00bac1
Closes-Bug: #1259867
Fix and enable gating on H402

Summary docstrings should end with punctuation.
Also changed it to command-style in a few places.

Change-Id: Id94fe995aa05356106ad09899b0ada27d608ff21
Do not clone non-raw images in rbd backend

RBD backend only supports booting from images in raw format. A volume
that was cloned from an image in any other format is not bootable. The
RBD driver will consider non-raw images to be uncloneable to trigger
automatic conversion to raw format.

Includes conversion of the corresponding unit test to use mock (instead
of mox) and expanded comments and error messages based on change #58893
by Edward Hope-Morley.

Change-Id: I5725d2f7576bc1b3e9b874ba944ad17d33a6e2cb
Closes-Bug: #1246219
Closes-Bug: #1247998
make delete recovery messages debug level

lvm.delete has recovery logic within it to do a second attempt
if it should fail the first time. It is currently however logging
those second attempts at error and warn levels. However, as this
is normal flow these should be debug level instead.

This is currently causing a few resets in the gate because this
is a non whitelisted error.

Change-Id: Ie684331d9d97c089ec23569d06981e90eb7f6a67
Closes-Bug: #1261731
Merge "Fix KeyError while generating a WSGI response"
Merge "make delete recovery messages debug level"
Add exception logging if flow creation fails

If the create_XYZ_flow fails in being created
its useful to log exactly what the error was in
detail (instead of trapping it and only raising
a generic error). The more detailed error shows
what the real problem was during the flows
construction (which usually is some larger
problem).

Change-Id: I9cd6b8e2c6298d8791ba3063be78f9b4c4a7c5d0
Merge "Fix and enable gating on H402"
Merge "Do not clone non-raw images in rbd backend"
Merge "Add exception logging if flow creation fails"