I confirmed that `add_version(...)` itself calls `str(...)` on the argument that
`things_version` is passed in to under both the Python 2.7 and Python 3.6 version of the
library so this is unnecessary here.
This results in an empty diff in py3 tests output.
The exception this addresses was preventing the test runner from running to completion
under Python 3, thus preventing using the full test suite to evaluate the impact of
porting efforts.
This change causes no regressions in the test suite under python 2.7 and only affects
tests AFAICT. I added debug logging to check all the strings that seem to make it to
that point and I didn't see anything that looked like it needed to be decoded in
particular, so I think this change is relatively safe.
The traceback for reference
```
Traceback (most recent call last):
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/bin/trial", line 8, in <module>
sys.exit(run())
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/scripts/trial.py", line 621, in run
test_result = trialRunner.run(suite)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 998, in run
return self._runWithoutDecoration(test, self._forceGarbageCollection)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 1025, in _runWithoutDecoration
run()
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 1020, in <lambda>
run = lambda: suite.run(result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 253, in run
TestSuite.run(self, result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/_asyncrunner.py", line 38, in run
test(result)
File "/usr/lib/python3.6/unittest/suite.py", line 84, in __call__
return self.run(*args, **kwds)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 212, in run
super(LoggedSuite, self).run(result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/_asyncrunner.py", line 38, in run
test(result)
File "/usr/lib/python3.6/unittest/suite.py", line 84, in __call__
return self.run(*args, **kwds)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 185, in run
test(result)
File "/usr/lib/python3.6/unittest/suite.py", line 84, in __call__
return self.run(*args, **kwds)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 185, in run
test(result)
File "/usr/lib/python3.6/unittest/suite.py", line 84, in __call__
return self.run(*args, **kwds)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/runner.py", line 185, in run
test(result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/_asyncrunner.py", line 59, in __call__
return self.run(result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/twisted/trial/_asyncrunner.py", line 69, in run
reporter._AdaptedReporter(result, self.__class__))
File "/home/rpatterson/src/work/sfu/tahoe-lafs/.tox/py36/lib/python3.6/site-packages/testtools/testcase.py", line 675, in run
return run_test.run(result)
File "/home/rpatterson/src/work/sfu/tahoe-lafs/src/allmydata/test/eliotutil.py", line 110, in run_and_republish
with RUN_TEST(name=self.id().decode("utf-8")).context() as action:
AttributeError: 'str' object has no attribute 'decode'
```
There were originally two versions of this, one in common and another in
common_util. We moved both into common_py3 but then removed the one from
common, so here we move back to common_util, while allowing imports from
common to avoid a noisy changeset.
