>>> has_c()
False
>>> b'\xed\xbc\xad'.decode('utf-8')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xed in position 0: invalid continuation byte
>>> from bson import encode, decode
>>> data = encode({'a':Regex(b'\xed\xbc\xad','')})
b'\r\x00\x00\x00\x0ba\x00\xed\xbc\xad\x00\x00\x00'
>>> decode(data)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 903, in decode
    return _bson_to_dict(data, codec_options)
bson.errors.InvalidBSON: 'utf-8' codec can't decode byte 0xed in position 0: invalid continuation byte
>>> decode(data, codec_options=CodecOptions(unicode_decode_error_handler='replace'))
{'a': Regex('���', 0)}

>>> encode({'a':Regex(b'\xed\xbc\xad')})
Traceback (most recent call last):
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 479, in _make_c_string_check
    _utf_8_decode(string, None, True)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xed in position 0: invalid continuation byte

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 871, in encode
    return _dict_to_bson(document, check_keys, codec_options)
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 808, in _dict_to_bson
    elements.append(_element_to_bson(key, value,
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 794, in _element_to_bson
    return _name_value_to_bson(name, value, check_keys, opts)
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 736, in _name_value_to_bson
    return _ENCODERS[type(value)](name, value, check_keys, opts)
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 610, in _encode_regex
    return b"\x0B" + name + _make_c_string_check(value.pattern) + b"\x00"
  File "/Users/shane/git/mongo-python-driver/bson/__init__.py", line 482, in _make_c_string_check
    raise InvalidStringData("strings in documents must be valid "
bson.errors.InvalidStringData: strings in documents must be valid UTF-8: b'\xed\xbc\xad'