Fix swiftclient.client.quote() for Python 3

On Python 3, urllib.parse.quote() accepts bytes and str (unicode) types and
always return str (unicode).

Add also more tests with non-ASCII characters.

Change-Id: I8e0f19da7240e874392327d0da074ed4abb7d213
Fix test_multithreading on Python 3

* On Python 3, the printer doesn't encode Unicode to utf8 anymore, since
  print() expects a Unicode string.

* Update unit tests for Python 3 since repr() doesn't escape non-ASCII
  characters in Unicode strings anymore:
  http://legacy.python.org/dev/peps/pep-3138/

Change-Id: I89471019d691a46651312d6a49964b719192148a
Merge "Fix swiftclient.client.quote() for Python 3"
Merge "Fix test_multithreading on Python 3"