py3: add a __str__ method to Abort This improves the rendering of some exceptions by avoiding raw bytestrings, especially when using --traceback option.

py3: add Python 3 exception output to test-lfs-serve-access.t Similar to a973a75e92bf or 3e9c6cef949b.

automation: install black This should unblock us from running the code formatting test in our automated environment. Differential Revision: https://phab.mercurial-scm.org/D7197

py3: use %d to format an int Avoids a TypeError under py3. Fortunately this is very much an edge case since it requires the user to have deliberately created a local tag of the form 'D\d+' that isn't truthful. Differential Revision: https://phab.mercurial-scm.org/D7215

fsmonitor: normalize exception types to bytes Unavailable.msg should now always be bytes. We also rename Unavailable.__str__ to __bytes__ as it always returns bytes. We make __str__ a simple wrapper that decodes that result to str. There's probably some excessive strutil.forcebytestr() in fsmonitor/__init__.py now. But at least the exceptions around type coercion should now be gone. Differential Revision: https://phab.mercurial-scm.org/D7214

fsmonitor: normalize clock value to bytes We normalize the value returned by watchman because we perform a number of compares with this value in code. So the easiest path forward is to normalize to bytes so we don't have to update many call sites. With this commit, the fsmonitor extension appears to be working with Python 3! Although there are still some failures in edge cases... Differential Revision: https://phab.mercurial-scm.org/D7213

fsmonitor: use next() instead of .next() This is needed for Python 3 compatibility. Differential Revision: https://phab.mercurial-scm.org/D7212