>>> re.compile('(?P=<foo>)')
= bad character in backref group name '<foo>' at position 4
+ bad character in group name '<foo>' at position 4

>>> re.compile('foo[a-')
= unexpected end of regular expression at position 6
+ bad character range a- at position 4

>>> re.compile('[')
= unexpected end of regular expression at position 1
+ unterminated character set at position 0

>>> re.compile('[^')
= unexpected end of regular expression at position 2
+ unterminated character set at position 0

>>> re.compile('[a')
= unexpected end of regular expression at position 2
+ unterminated character set at position 0

>>> re.compile('[a-')
= unexpected end of regular expression at position 3
+ bad character range a- at position 1

>>> re.compile('[\\w-b]')
= bad character range at position 4
+ bad character range \w-b at position 1

>>> re.compile('[a-\\w]')
= bad character range at position 3
+ bad character range a-\w at position 1

>>> re.compile('[b-a]')
= bad character range at position 3
+ bad character range b-a at position 1

>>> re.compile('(')
= unbalanced parenthesis at position 1
+ missing ), unterminated subpattern at position 0

>>> re.compile('((a|b)')
= unbalanced parenthesis at position 6
+ missing ), unterminated subpattern at position 0

>>> re.compile('(?z)')
= unexpected end of pattern at position 3
+ unknown extension ?z at position 1

>>> re.compile('(?iz)')
= unknown extension at position 3
+ unknown flag at position 3

>>> re.compile('(?i')
= unexpected end of pattern at position 3
+ missing ) at position 3

>>> re.compile('(?#abc')
= unbalanced parenthesis at position 6
+ missing ), unterminated comment at position 0

>>> re.compile('(?<')
= syntax error at position 3
+ unexpected end of pattern at position 3

>>> re.compile('(?<>)')
= syntax error at position 4
+ unknown extension ?<> at position 1

>>> re.compile('\\')
= bogus escape (end of line) at position 0
+ bad escape (end of pattern) at position 0

>>> re.compile('(abc\\1)')
= cannot refer to open group at position 4
+ cannot refer to an open group at position 4

>>> re.compile('()(?(1)a|b')
= unbalanced parenthesis at position 10
+ missing ), unterminated subpattern at position 2

>>> re.sub('()', '\\g<268435455>', 'xx')
- the group number is too large at position 3
+ invalid group reference at position 3

>>> re.compile('(?P<a>)(?(268435455))')
= the group number is too large at position 10
+ invalid group reference at position 10

>>> re.compile(b'[\\567]')
= octal escape value '\\567' outside of range 0-0o377 at position 1
+ octal escape value \567 outside of range 0-0o377 at position 1

>>> re.compile(b'[\\911]')
= bogus escape: '\\9' at position 1
+ bad escape \9 at position 1

>>> re.compile(b'[\\x1z]')
= bogus escape: '\\x1' at position 1
+ bad escape \x1 at position 1

>>> re.compile(b'\\567')
= octal escape value '\\567' outside of range 0-0o377 at position 0
+ octal escape value \567 outside of range 0-0o377 at position 0

>>> re.compile(b'\\911')
= bogus escape: '\\91' at position 0
+ invalid group reference at position 0

>>> re.compile(b'\\x1')
= bogus escape: '\\x1' at position 0
+ bad escape \x1 at position 0

>>> re.compile(b'\\x1z')
= bogus escape: '\\x1' at position 0
+ bad escape \x1 at position 0

>>> re.compile('[\\567]')
= octal escape value '\\567' outside of range 0-0o377 at position 1
+ octal escape value \567 outside of range 0-0o377 at position 1

>>> re.compile('[\\911]')
= bogus escape: '\\9' at position 1
+ bad escape \9 at position 1

>>> re.compile('[\\x1z]')
= bogus escape: '\\x1' at position 1
+ bad escape \x1 at position 1

>>> re.compile('[\\u123z]')
= bogus escape: '\\u123' at position 1
+ bad escape \u123 at position 1

>>> re.compile('[\\U0001234z]')
= bogus escape: '\\U0001234' at position 1
+ bad escape \U0001234 at position 1

>>> re.compile('[\\U00110000]')
= bogus escape: '\\U00110000' at position 1
+ bad escape \U00110000 at position 1

>>> re.compile('\\567')
= octal escape value '\\567' outside of range 0-0o377 at position 0
+ octal escape value \567 outside of range 0-0o377 at position 0

>>> re.compile('\\911')
= bogus escape: '\\91' at position 0
+ invalid group reference at position 0

>>> re.compile('\\x1')
= bogus escape: '\\x1' at position 0
+ bad escape \x1 at position 0

>>> re.compile('\\x1z')
= bogus escape: '\\x1' at position 0
+ bad escape \x1 at position 0

>>> re.compile('\\u123')
= bogus escape: '\\u123' at position 0
+ bad escape \u123 at position 0

>>> re.compile('\\u123z')
= bogus escape: '\\u123' at position 0
+ bad escape \u123 at position 0

>>> re.compile('\\U0001234')
= bogus escape: '\\U0001234' at position 0
+ bad escape \U0001234 at position 0

>>> re.compile('\\U0001234z')
= bogus escape: '\\U0001234' at position 0
+ bad escape \U0001234 at position 0

>>> re.compile('\\U00110000')
= bogus escape: '\\U00110000' at position 0
+ bad escape \U00110000 at position 0

>>> re.sub('x', '\\400', 'x')
- octal escape value '\\400' outside of range 0-0o377 at position 0
+ octal escape value \400 outside of range 0-0o377 at position 0

>>> re.sub('x', '\\777', 'x')
- octal escape value '\\777' outside of range 0-0o377 at position 0
+ octal escape value \777 outside of range 0-0o377 at position 0

>>> re.compile('(?Pxy)')
= unknown specifier: ?Px at position 3
+ unknown extension ?Px

>>> re.compile('(?P<a>)(?P=a')
= unterminated name at position 12
+ missing ), unterminated name at position 11

>>> re.compile('(?P=')
= unterminated name at position 4
+ missing group name at position 4

>>> re.compile('(?P=1)')
= bad character in backref group name '1' at position 4
+ bad character in group name '1' at position 4

>>> re.compile('(?P=a)')
= unknown group name: 'a' at position 4
+ unknown group name 'a'

>>> re.compile('(?P=a1)')
= unknown group name: 'a1' at position 4
+ unknown group name 'a1'

>>> re.compile('(?P=a.)')
= bad character in backref group name 'a.' at position 4
+ bad character in group name 'a.' at position 4

>>> re.compile('(?P<)')
= unterminated name at position 5
+ missing >, unterminated name at position 4

>>> re.compile('(?P<a')
= unterminated name at position 5
+ missing >, unterminated name at position 4

>>> re.compile('(?P<')
= unterminated name at position 4
+ missing group name at position 4

>>> re.compile('(?(')
= unterminated name at position 3
+ missing group name at position 3

>>> re.compile('(?(a))')
= unknown group name: 'a' at position 3
+ unknown group name 'a' at position 3

>>> re.compile('(?(-1))')
= bad character in group name at position 3
+ bad character in group name '-1' at position 3

>>> re.compile('(?(1a))')
= bad character in group name at position 3
+ bad character in group name '1a' at position 3

>>> re.compile('(?(a.))')
= bad character in group name at position 3
+ bad character in group name 'a.' at position 3

>>> re.sub('(?P<a>x)', '\\g<a', 'xx')
- unterminated name at position 4
+ missing >, unterminated name at position 3

>>> re.sub('(?P<a>x)', '\\g<', 'xx')
- unterminated name at position 3
+ missing group name at position 3

>>> re.sub('(?P<a>x)', '\\g', 'xx')
- missing group name at position 1
+ missing < at position 2

>>> re.sub('(?P<a>x)', '\\g<a a>', 'xx')
- bad character in group name at position 3
+ bad character in group name 'a a' at position 3

>>> re.sub('(?P<a>x)', '\\g<1a1>', 'xx')
- bad character in group name at position 3
+ bad character in group name '1a1' at position 3

>>> re.sub('(?P<a>x)', '\\g<-1>', 'xx')
- negative group number at position 3
+ bad character in group name '-1' at position 3

>>> re.sub('(?P<a>x)', '\\g<©>', 'xx')
- bad character in group name at position 3
+ bad character in group name '©' at position 3