[GHC] #4806: Make error message more user friendly when module is not found because package is unusable

[GHC]

#4806: Make error message more user friendly when module is not found because
package is unusable
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        Reporter:  mitar             |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.0.1
      Resolution:                    |             Keywords:  newcomer
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgillespie):

 I think the strategy should be to modify mkModuleToPkgConfAll to include
 all UnusablePackages in PackageState.hs. We could then add another
 constructor to ModuleOrigin (say, BrokenPackage) so that we could report
 it on lookupModuleWithSuggestions.

 Please correct me if this is not a reasonable approach.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4806#comment:24>
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