test: fail for missing output files

Instead of ignoring missing `.out` files for message/pseudo-tty tests,
raise an error to indicate that something is not quite right.

Ref: https://github.com/nodejs/node/pull/10037
PR-URL: https://github.com/nodejs/node/pull/10150
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

test/message/testcfg.py

@@ -127,8 +127,7 @@ class MessageTestConfiguration(test.TestConfiguration):
         file_path = file_prefix + ".js"
         output_path = file_prefix + ".out"
         if not exists(output_path):
-          print "Could not find %s" % output_path
-          continue
+          raise Exception("Could not find %s" % output_path)
         result.append(MessageTestCase(test, file_path, output_path,
                                       arch, mode, self.context, self))
     return result

test/pseudo-tty/testcfg.py

@@ -142,8 +142,7 @@ class TTYTestConfiguration(test.TestConfiguration):
         file_path = file_prefix + ".js"
         output_path = file_prefix + ".out"
         if not exists(output_path):
-          print "Could not find %s" % output_path
-          continue
+          raise Exception("Could not find %s" % output_path)
         result.append(TTYTestCase(test, file_path, output_path,
                                       arch, mode, self.context, self))
     return result