Python 3.7 support

[jamesjer]

The Fedora Linux distribution has started building packages with a prerelease of python 3.7, to catch problems early. The manuel package build fails like this:

======================================================================
FAIL: /builddir/build/BUILD/python-manuel-1.9.0/python3-manuel-1.9.0/src/manuel/README.txt:Parsing
/builddir/build/BUILD/python-manuel-1.9.0/python3-manuel-1.9.0/src/manuel/README.txt:Parsing

Traceback (most recent call last):
File "/builddir/build/BUILD/python-manuel-1.9.0/python3-manuel-1.9.0/src/manuel/testing.py", line 48, in runTest
'\n' + DIVIDER + DIVIDER.join(results))
AssertionError:

File "/builddir/build/BUILD/python-manuel-1.9.0/python3-manuel-1.9.0/src/manuel/README.txt", line 83, in README.txt
Failed example:
region.start_match
Expected:
<_sre.SRE_Match object...>
Got:
<re.Match object; span=(44, 56), match='one: 1, 2, 3'>

File "/builddir/build/BUILD/python-manuel-1.9.0/python3-manuel-1.9.0/src/manuel/README.txt", line 85, in README.txt
Failed example:
region.end_match
Expected:
<_sre.SRE_Match object...>
Got:
<re.Match object; span=(70, 84), match='three: 3, 5, 1'>

[jvalleroy]

This issue is fixed in #13. One remaining task, is to add python 3.6 and 3.7 to CI tests.

[icemac]

This ticket can be closed @strichter fixed it in 22a109c.