Deprecated issue with regex declarations on re.compile strings

[timmyreynolds]

Incorrect/Correct syntax by example:

# Incorrect Syntax, missing 'r' prefix
import re
DEF = re.compile('foo\sbar')

# Correct Syntax, includes 'r' prefix
import re
DEF = re.compile(r'foo\sbar')

Affected files:

• pony/orm/dbproviders/oracle.py
• pony/orm/dbapiprovider.py
• pony/thirdparty/decorator.py
• pony/converting.py