Backward compatibility with Coverage 5.0

[ryabchi]

Hello!

14 December was officially released library: coverage 5.0 version. The release violated backward compatibility with teamcity-messages 1.27.

Reason

teamcity-messages tries import from coverage.report import Reporter in pytest_plugin.py#L377 But this is no longer present in Coverage 5.0 library.

New coverage.report interface: report.py

Error

As result I have next error in my builds:

[Step 1/2] Coverage statistics reporting failed
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/teamcity/pytest_plugin.py", line 371, in pytest_terminal_summary
    self._report_coverage()
  File "/usr/local/lib/python3.7/site-packages/teamcity/pytest_plugin.py", line 378, in _report_coverage
    from coverage.report import Reporter
ImportError: cannot import name 'Reporter' from 'coverage.report' (/usr/local/lib/python3.7/site-packages/coverage/report.py)