add valid mimetype for .py files

[MarcelGeo]

• we are validating .py files by extension -> validate also mime type for such a files

[coveralls]

Pull Request Test Coverage Report for Build 17912683650

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.318%

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Totals
Change from base Build 17905350944:	0.0%
Covered Lines:	7553
Relevant Lines:	8008

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💛 - Coveralls