Never catch a bare except clause

While investigating aws/aws-cli#628 I noticed that I'd still
occasionally get tracebacks, particularly a DataNotFoundError
from botocore's base.py module.  After further investigation,
this was because the bare except clauses were catching the
KeyboardInterrupts and swallowing them.  This resulted in a
traceback somewhere downstream.

The specific error I hit from aws/aws-cli#628 was from base.py,
but I did a quick search through the code and for the time being
at least replaced the bare excepts with except Exception.  There's
potential to switch some of these to more specific exceptions later.
Merge branch 'no-bare-excepts' into develop

* no-bare-excepts:
  Never catch a bare except clause
Update route53 to the latest model
Bumping version to 0.33.0
Merge branch 'release-0.33.0' into develop

* release-0.33.0:
  Bumping version to 0.33.0
  Update route53 to the latest model
fix json -> xml request payload conversion

When creating request payload from json data, json `null` will now be converted to empty string '' not string 'None'.
Merge branch 'quiver-fix-json-to-request-payload' into develop

* quiver-fix-json-to-request-payload:
  fix json -> xml request payload conversion