[Pharo-project] [update 2.0] #20250

[Esteban Lorenzano]

20250
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Issue 6503:     ScriptLoader deletePackage: does not say what it says
        http://code.google.com/p/pharo/issues/detail?id=6503
        
Issue 6542:     unload package Polymorph
        http://code.google.com/p/pharo/issues/detail?id=6542
        
Issue 6544:     [ENH]: SystemPreferences - Notify Errors
        http://code.google.com/p/pharo/issues/detail?id=6544
        
Issue 6545:     There are no accesses to commandLine in CommandLineHandlerTest
        http://code.google.com/p/pharo/issues/detail?id=6545