Unicode support problems (for spec files and in some situations for modules under test)

[Stvad]

Mamba seems to be trying to read the spec files decoding them using ascii decoder leading to problems when spec file contain any unicode character.

Minimal example to reproduce:

from mamba import description, it

with description("Spec"):
    with it("Should not fail 🤔"):
        pass

This is going to lead to the following error when trying to run it:

Traceback (most recent call last):
  File "/Users/sitalov/Dropbox/SoftwareEngineering/Projects/Anki/CrowdAnki/test/mamba_runner.py", line 3, in <module>
    main()
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/cli.py", line 18, in main
    runner.run()
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/runners.py", line 29, in run
    modules = self.example_collector.modules()
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/example_collector.py", line 25, in modules
    with self._load_module_from(path) as module:
  File "/Users/sitalov/.pyenv/versions/3.6.8/lib/python3.6/contextlib.py", line 81, in __enter__
    return next(self.gen)
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/example_collector.py", line 57, in _load_module_from
    yield self._module_from_ast(name, path)
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/example_collector.py", line 60, in _module_from_ast
    tree = self._parse_and_transform_ast(path)
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/site-packages/mamba/example_collector.py", line 82, in _parse_and_transform_ast
    tree = ast.parse(f.read(), filename=path)
  File "/Users/sitalov/.local/share/virtualenvs/CrowdAnki-uIF4Vw2q/lib/python3.6/encodings/ascii.py", line 26, in decode
    return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xf0 in position 90: ordinal not in range(128)