UnicodeDecodeError: 'utf8' codec can't decode byte 0xe2 in position 652952: invalid continuation byte after building latex docs

[asmeurer]

From https://github.com/sympy/sympy/pull/1660#issuecomment-10547218.

I tried to run ./sympy-bot review 1660 -D --build-docs-command " make clean && make html-errors && make clean && make latex && cd _build/latex && make all", but after it built the latex, I got

Traceback (most recent call last):
  File "./sympy-bot", line 706, in <module>
    main()
  File "./sympy-bot", line 248, in main
    dispatch_reviews(options, urls, username=username, password=password, token=token)
  File "./sympy-bot", line 548, in dispatch_reviews
    config.build_docs_command, False, merge_commit)
  File "/Users/aaronmeurer/Documents/Python/sympy/sympy-bot/utils/testrunner.py", line 42, in run_tests
    log, r = cmd2(test_command, cwd=master_repo_path)
  File "/Users/aaronmeurer/Documents/Python/sympy/sympy-bot/utils/cmd.py", line 55, in cmd2
    log = log.decode(sys.stdout.encoding)
  File "/sw/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xe2 in position 652952: invalid continuation byte