Do not blow up when something fails when running a directory

lib/m/parser.rb

@@ -28,8 +28,13 @@ def parse
             t.test_files = FileList["#{testable.file}/*test*.rb", "#{testable.file}/*spec*.rb"]
           end
           # Invoke the rake task and exit, hopefully it'll work!
-          Rake::Task['m_custom'].invoke
-          exit
+          begin
+            Rake::Task['m_custom'].invoke
+          rescue RuntimeError
+            exit
+          ensure
+            exit
+          end
         else
           return testable
         end

test/everything_test.rb

@@ -21,6 +21,11 @@ def test_running_tests_within_a_subdirectory
     assert_output(/12 tests/, output)
   end
 
+  def test_running_tests_with_failures_within_a_subdirectory
+    output = m('examples/subdir_with_failures')
+    assert_output(/1 tests, 1 assertions, 1 failures/, output)
+  end
+
   def test_blank_file_is_quieter
     output = m('bananas')
     assert(/Valid tests to run/ !~ output)

test/examples/subdir_with_failures/a_test.rb

@@ -0,0 +1,7 @@
+require_relative '../../test_helper'
+
+class ATest < MTest
+  def test_a
+    assert_equal 1, 2
+  end
+end