fix - Display error alert when remove user from orga failed

[martinlehoux]

Object

• Fixes #160 .
• As the back end doesn't send a message explaining the HTTP 403 error, it just use js alert to warn the user.
• I didn't find any way already implemented to handle error messages display in the front, that is why I decided to use alert.
• [x] Translation
• [ ] Translation compilation
• Feel free to comment if you have a better solution.

Test

• Tested with docker-compose on Mac OS.

[martinlehoux]

@fallen I've updated the PR :)

[fallen]

Merged in:

• https://github.com/pytition/Pytition/commit/e649b1c6a1cdaa71d1370e637d32dfd499d4fdc7
• https://github.com/pytition/Pytition/commit/dcbac0c01ff188988141baf2ea59ebefa37a8129