[lit] Fix undefined symbol ArgumentError

[modocache]

Summary

ArgumentError is not defined by the Python standard library.
Executing this line of code would throw a exception, but not the
intended one. It would throw a NameError exception, since ArgumentError
is undefined.

Use ValueError instead, which is defined by the Python standard
library.

utils/lit/lit/Test.py

def __init__(self, suite, path_in_suite, config, file_path = None):
         # can optionally be provided by test format handlers, and will be
         # honored when the test result is supplied.
         self.xfails = []
         # The test result, once complete.
         self.result = None
 
     def setResult(self, result):
         if self.result is not None:
-            raise ArgumentError("test result already set")
+            raise ValueError("test result already set")
         if not isinstance(result, Result):
-            raise ArgumentError("unexpected result type")
+            raise ValueError("unexpected result type")
 
         self.result = result
 
         # Apply the XFAIL handling to resolve the result exit code.
         if self.isExpectedToFail():
             if self.result.code == PASS:
                 self.result.code = XPASS
             elif self.result.code == FAIL: