...
code, flags, groupcount, groupindex, indexgroup, group_offsets = regexp.compile(cache, source, flags)
File "topaz/utils/regexp.py", line 1300, in compile
cache.set(pattern, flags, _compile_no_cache(pattern, flags))
File "topaz/utils/regexp.py", line 1285, in _compile_no_cache
parsed = parsed.optimize(info)
File "topaz/utils/regexp.py", line 604, in optimize
prefix, branches = self._split_common_prefix(info, branches)
File "topaz/utils/regexp.py", line 491, in _split_common_prefix
while (pos < end_pos and prefix[pos].can_be_affix() and
AttributeError: 'AtPosition' object has no attribute 'can_be_affix'