Simplify conditions for CoreAssertion initialization

tool/lib/core_assertions.rb

@@ -24,13 +24,11 @@ module Test
     end
 
     module CoreAssertions
-      if defined?(MiniTest)
       require_relative 'envutil'
+
+      if defined?(MiniTest)
         # for ruby core testing
         include MiniTest::Assertions
-
-        # Compatibility hack for assert_raise
-        Test::Unit::AssertionFailedError = MiniTest::Assertion
       else
         module MiniTest
           class Assertion < Exception; end
@@ -38,7 +36,6 @@ module Test
         end
 
         require 'pp'
-        require_relative 'envutil'
         include Test::Unit::Assertions
       end
 

tool/lib/test/unit/assertions.rb

@@ -303,5 +303,9 @@ EOT
         template.gsub(/\G((?:[^\\]|\\.)*?)(\\)?\?/) { $1 + ($2 ? "?" : mu_pp(arguments.shift)) }
       end
     end
+
+    # Compatibility hack for assert_raise
+    AssertionFailedError = MiniTest::Assertion
+
   end
 end