It's a bit frustrating not to be able to catch 
exceptions raised by re.compile with just the re 
module.  The fact that sre_constants.error is 
raised is a bit too much implementation showing 
through, IMO. 
 
Anyway, I suggest a exception be added to the re 
module that subclasses sre_constants.error for 
backwards compatibility.  So users can simply 
import re and catch re.error instead of having to 
import re and sre_constants and catch 
sre_constants.error.