Remove InstallationError superclass

None of these subclasses share any behavior other than what is inherited
from RuntimeError, so we can just get rid of the superclass.

Library/Homebrew/exceptions.rb

@@ -79,46 +79,33 @@ class OperationInProgressError < RuntimeError
   end
 end
 
-module Homebrew
-  class InstallationError < RuntimeError
-    attr_reader :formula
-
-    def initialize(formula, message)
-      super message
-      @formula = formula
-    end
-  end
-end
-
 class CannotInstallFormulaError < RuntimeError; end
 
 class FormulaAlreadyInstalledError < RuntimeError; end
 
-class FormulaInstallationAlreadyAttemptedError < Homebrew::InstallationError
+class FormulaInstallationAlreadyAttemptedError < RuntimeError
   def initialize(formula)
-    super formula, "Formula installation already attempted: #{formula}"
+    super "Formula installation already attempted: #{formula}"
   end
 end
 
-class UnsatisfiedRequirements < Homebrew::InstallationError
-  attr_reader :reqs
-
-  def initialize formula, reqs
-    @reqs = reqs
-    message = (reqs.length == 1) \
-                ? "An unsatisfied requirement failed this build." \
-                : "Unsatisifed requirements failed this build."
-    super formula, message
+class UnsatisfiedRequirements < RuntimeError
+  def initialize(reqs)
+    if reqs.length == 1
+      super "An unsatisfied requirement failed this build."
+    else
+      super "Unsatisified requirements failed this build."
+    end
   end
 end
 
-class FormulaConflictError < Homebrew::InstallationError
-  attr_reader :conflicts
+class FormulaConflictError < RuntimeError
+  attr_reader :formula, :conflicts
 
   def initialize(formula, conflicts)
-    @conflicts = conflicts
     @formula = formula
-    super formula, message
+    @conflicts = conflicts
+    super message
   end
 
   def conflict_message(conflict)
@@ -144,13 +131,14 @@ class FormulaConflictError < Homebrew::InstallationError
   end
 end
 
-class BuildError < Homebrew::InstallationError
-  attr_reader :env
+class BuildError < RuntimeError
+  attr_reader :formula, :env
 
   def initialize(formula, cmd, args, env)
+    @formula = formula
     @env = env
     args = args.map{ |arg| arg.to_s.gsub " ", "\\ " }.join(" ")
-    super formula, "Failed executing: #{cmd} #{args}"
+    super "Failed executing: #{cmd} #{args}"
   end
 
   def issues
@@ -202,9 +190,9 @@ end
 
 # raised by CompilerSelector if the formula fails with all of
 # the compilers available on the user's system
-class CompilerSelectionError < Homebrew::InstallationError
-  def initialize formula
-    super formula, <<-EOS.undent
+class CompilerSelectionError < RuntimeError
+  def initialize(formula)
+    super <<-EOS.undent
       #{formula.name} cannot be built with any available compilers.
       To install this formula, you may need to:
         brew install gcc

Library/Homebrew/formula_installer.rb

@@ -232,7 +232,7 @@ class FormulaInstaller
       end
     end
 
-    raise UnsatisfiedRequirements.new(f, fatals) unless fatals.empty?
+    raise UnsatisfiedRequirements.new(fatals) unless fatals.empty?
   end
 
   def install_requirement_default_formula?(req, build)