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Hi,
I would like to make a small improvement to the exception raised when _compile() function fails with exception on line 245. 
Please see attached amended file. The line of code is amended from: 
 raise error, v # invalid expression
to:
 raise error, r'%s with pattern: %s' % (v, pattern) # invalid expression
As this is my first contribution, please let me know if this is the correct procedure to submit changes.
Kind regards,
Ling