Modify unit tests to distinguish between FAIL and ERROR. Move comparison utilities into our derived unit test class.

compiler/debug.py

@@ -14,14 +14,13 @@ def check(check,str):
      index) = inspect.getouterframes(inspect.currentframe())[1]
     if not check:
         print("ERROR: file {0}: line {1}: {2}".format(os.path.basename(filename),line_number,str))
-        sys.exit(-1)
+        assert 0
 
-def error(str,return_value=None):
+def error(str,return_value):
     (frame, filename, line_number, function_name, lines,
      index) = inspect.getouterframes(inspect.currentframe())[1]
     print("ERROR: file {0}: line {1}: {2}".format(os.path.basename(filename),line_number,str))
-    if return_value:
-        sys.exit(return_value)
+    assert return_value==0
 
 def warning(str):
     (frame, filename, line_number, function_name, lines,