Issue 3231: re.compile fails with some bytes patterns

Some patterns can be compiled in str form but not in bytes form. This
was overlooked because the test suite wasn't correctly adapted for py3k:

>>> re.compile('[\\1]')
<_sre.SRE_Pattern object at 0xb7be1410>
>>> re.compile('\\09')
<_sre.SRE_Pattern object at 0xb7c4f2f0>
>>> re.compile('\\n')
<_sre.SRE_Pattern object at 0xb7be1f50>

but:

>>> re.compile(b'[\\1]')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 188, in compile
return _compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 240, in _compile
p = sre_compile.compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_compile.py", line 497, in
compile
p = sre_parse.parse(p, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 685, in parse
p = _parse_sub(source, pattern, 0)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 320, in
_parse_sub
itemsappend(_parse(source, state))
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 409, in _parse
this = sourceget()
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 215, in get
self.__next()
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 204, in __next
char = char + c
TypeError: Can't convert 'int' object to str implicitly
>>> re.compile(b'\\09')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 188, in compile
return _compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 240, in _compile
p = sre_compile.compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_compile.py", line 497, in
compile
p = sre_parse.parse(p, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 678, in parse
source = Tokenizer(str)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 187, in
__init__
self.__next()
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 204, in __next
char = char + c
TypeError: Can't convert 'int' object to str implicitly
>>> re.compile(b'\\n')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 188, in compile
return _compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/re.py", line 240, in _compile
p = sre_compile.compile(pattern, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_compile.py", line 497, in
compile
p = sre_parse.parse(p, flags)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 678, in parse
source = Tokenizer(str)
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 187, in
__init__
self.__next()
  File "/home/antoine/py3k/reunicode/Lib/sre_parse.py", line 204, in __next
char = char + c
TypeError: Can't convert 'int' object to str implicitly