coalaTest: Use bear_test_module() in coala -A test
coalaTest: Use bear_test_module() in coala -A test

When testing coala -A we do not want other bear modules which have
errors to make the test fail. Hence, we force it to only use
the `test_bears` module which we have.

This is done using the contextmanager bear_test_module() which overrides
the pkg_resources end-point finding utility.

Fixes https://github.com/coala-analyzer/coala/issues/2055

netman92/coala,yashtrivedi96/coala,kartikeys98/coala,meetmangukiya/coala,stevemontana1980/coala,Shade5/coala,Balaji2198/coala,ayushin78/coala,aptrishu/coala,Shade5/coala,JohnS-01/coala,CruiseDevice/coala,SanketDG/coala,NalinG/coala,netman92/coala,NalinG/coala,refeed/coala,arjunsinghy96/coala,coala-analyzer/coala,aptrishu/coala,RJ722/coala,Asnelchristian/coala,MariosPanag/coala,vinc456/coala,sophiavanvalkenburg/coala,impmihai/coala,JohnS-01/coala,mr-karan/coala,ManjiriBirajdar/coala,kartikeys98/coala,MariosPanag/coala,Nosferatul/coala,meetmangukiya/coala,vinc456/coala,rimacone/testing2,d6e/coala,arush0311/coala,CruiseDevice/coala,arjunsinghy96/coala,Balaji2198/coala,coala-analyzer/coala,Nosferatul/coala,ayushin78/coala,scottbelden/coala,NalinG/coala,shreyans800755/coala,shreyans800755/coala,tltuan/coala,NalinG/coala,incorrectusername/coala,nemaniarjun/coala,Asnelchristian/coala,Asalle/coala,Asalle/coala,incorrectusername/coala,yashLadha/coala,Nosferatul/coala,rimacone/testing2,d6e/coala,aptrishu/coala,sophiavanvalkenburg/coala,meetmangukiya/coala,scottbelden/coala,karansingh1559/coala,ayushin78/coala,ManjiriBirajdar/coala,nemaniarjun/coala,yashLadha/coala,kartikeys98/coala,arush0311/coala,RJ722/coala,nemaniarjun/coala,coala/coala,netman92/coala,NiklasMM/coala,impmihai/coala,sagark123/coala,abhiroyg/coala,sophiavanvalkenburg/coala,Shade5/coala,jayvdb/coala,scottbelden/coala,mr-karan/coala,coala-analyzer/coala,yashLadha/coala,sils1297/coala,MariosPanag/coala,damngamerz/coala,NalinG/coala,NalinG/coala,Asalle/coala,jayvdb/coala,NiklasMM/coala,yashtrivedi96/coala,tltuan/coala,stevemontana1980/coala,JohnS-01/coala,tltuan/coala,arush0311/coala,jayvdb/coala,impmihai/coala,stevemontana1980/coala,incorrectusername/coala,sils1297/coala,tushar-rishav/coala,karansingh1559/coala,tushar-rishav/coala,CruiseDevice/coala,rimacone/testing2,karansingh1559/coala,sils1297/coala,NiklasMM/coala,refeed/coala,mr-karan/coala,ManjiriBirajdar/coala,yashtrivedi96/coala,coala/coala,RJ722/coala,Balaji2198/coala,arjunsinghy96/coala,shreyans800755/coala,vinc456/coala,SanketDG/coala,refeed/coala,abhiroyg/coala,sagark123/coala,coala/coala,sagark123/coala,Asnelchristian/coala,abhiroyg/coala,tushar-rishav/coala,SanketDG/coala,damngamerz/coala,d6e/coala,damngamerz/coala,NalinG/coala