Invoke super() in requirement subclasses

Library/Homebrew/requirements.rb

@@ -108,6 +108,7 @@ class MPIDependency < Requirement
     @lang_list = lang_list
     @non_functional = []
     @unknown_langs = []
+    super()
   end
 
   def mpi_wrapper_works? compiler
@@ -184,6 +185,7 @@ class ConflictRequirement < Requirement
     @formula = formula
     @name = name
     @opts = opts
+    super()
   end
 
   def message