Issue description:
The LDAP exception processing is hard to approach because of its string inconsistency.

Examples of the returned exception:

NO_SUCH_OBJECT('No object exists given the filter criteria demo')
INVALID_SYNTAX({'desc': 'Invalid syntax', 'info': 'autoMemberScope: value #0 invalid per syntax\n'})

Operating system:
Fedora 30

Python version:
3.7.4

python-ldap version:
3.1.0