get_dict_from_pyfile: ignore underscore variables

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (d6bf257) 95.88% compared to head (a9cb656) 95.88%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #164 +/- ## ======================================= Coverage 95.88% 95.88% ======================================= Files 36 36 Lines 2357 2357 Branches 437 438 +1 ======================================= Hits 2260 2260 Misses 75 75 Partials 22 22 ``` | [Impacted Files](https://codecov.io/gh/BEMServer/bemserver-core/pull/164?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer) | Coverage Δ | | |---|---|---| | [bemserver\_core/utils.py](https://codecov.io/gh/BEMServer/bemserver-core/pull/164?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer#diff-YmVtc2VydmVyX2NvcmUvdXRpbHMucHk=) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BEMServer)

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