Check and fallback to "en" to init wx.Locale

[dieterplex]

In #62, there is no locale "en_US.UTF-8" and causing wx to popup warning.

[sourcery-ai]

Sourcery Code Quality Report

Merging this PR leaves code quality unchanged.

Quality metrics	Before	After	Change
Complexity	2.30 ⭐	2.30 ⭐	0.00
Method Length	55.17 ⭐	55.17 ⭐	0.00
Working memory	5.40 ⭐	5.40 ⭐	0.00
Quality	81.67% ⭐	81.67% ⭐	0.00%

Other metrics	Before	After	Change
Lines	141	141	0

Changed files	Quality Before	Quality After	Quality Change
youtube_dl_gui/app.py	81.67% ⭐	81.67% ⭐	0.00%

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation

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[dieterplex]

Without available checking it still show warning for supported lang on a system missing the locale.

[oleksis]

How we can reproduce the issue? Can make one test for cover this case?

Remember we check the locale for use the catalogs for the GUI translations. In the PR you return the default value and verified. Any case you keep using wx.LANGUAGE_ENGLISH

[oleksis]

@dieterplex Thanks for spot the case

I thinks the idea is like this commit