* test/__init__.py: Put safe_repr import/implementation here so that it
is available to functional and unit tests.
* test/functional/swift_test_client.py: When a request fails
record why that request failed, how many requests failed, and what the
request was when raising RequestError to aid in debugging. Makes use of
safe_repr from test/__init__.py.
* test/unit/common/test_constraints.py: Remove implementation of
safe_repr and use the implementation in test/__init__.py.
Change-Id: I6c957343fb4b8b95d3875fd5ca87b3cf28a5f47a