When we received an error message from the Review Board API, if we didn't have a pre-generated string for that error code locally we would include the error body verbatim. We did this by attempting to cast it to a string and encode it to utf-8, but that only works on Python 2 where str is actually bytes. On Python 3, an error is raised becuase you are not allowed to decode a bytes object into text without a codec. Instead, we now return text from the API errors when calling `str(e)` on them, instead of returning their body verbatim. While I was here, I also removed a bunch of unnecessary unicode literals. We are using `unicode_literals` everywhere so they were redundant. Testing done: Confirmed the following hold on Python verisons 2.7, 3.5, 3.6, and 3.7: - With this entire patch stack (/r/10685, /r/10695, and /r/10696), `rbt post` is able to create review requests with commit history.