Solver: Remove unused FailReason constructor.

cabal-install/Distribution/Solver/Modular/Message.hs

@@ -124,7 +124,6 @@ showGR UserGoal            = " (user goal)"
 showGR (DependencyGoal dr) = " (dependency of " ++ showDependencyReason dr ++ ")"
 
 showFR :: ConflictSet -> FailReason -> String
-showFR _ InconsistentInitialConstraints   = " (inconsistent initial constraints)"
 showFR _ (Conflicting ds)                 = " (conflict: " ++ L.intercalate ", " (L.map showDep ds) ++ ")"
 showFR _ CannotInstall                    = " (only already installed instances can be used)"
 showFR _ CannotReinstall                  = " (avoiding to reinstall a package with same version but new dependencies)"

cabal-install/Distribution/Solver/Modular/Tree.hs

@@ -92,8 +92,7 @@ data Tree d c =
 data POption = POption I (Maybe PackagePath)
   deriving (Eq, Show)
 
-data FailReason = InconsistentInitialConstraints
-                | Conflicting [LDep QPN]
+data FailReason = Conflicting [LDep QPN]
                 | CannotInstall
                 | CannotReinstall
                 | Shadowed