better error/exception name for re.compile error. 

Currently the error raise by re.compile when it fails to compile is `error` defined in sre_constants.py: 

```
class error(Exception):
    """Exception raised for invalid regular expressions.

```

This is quite disturbing as most exception start with an uppercase and have a tiny bit more descriptive name. 

Would it be possible to have it renamed as something more explicit like `ReCompileError`, and still keeping the potential `error` alias as deprecated ?