Check the response to a command for errors.

def _check_command_response(response, msg=None, allowable_errors=None,
                            parse_write_concern_error=False):
    """Check the response to a command for errors.
    """
    if "ok" not in response:
        # Server didn't recognize our message as a command.
        raise OperationFailure(response.get("$err"),
                               response.get("code"),
                               response)

    # TODO: remove, this is moving to _check_gle_response
    if response.get("wtimeout", False):
        # MongoDB versions before 1.8.0 return the error message in an "errmsg"
        # field. If "errmsg" exists "err" will also exist set to None, so we
        # have to check for "errmsg" first.
        raise WTimeoutError(response.get("errmsg", response.get("err")),
                            response.get("code"),
                            response)

    if parse_write_concern_error and 'writeConcernError' in response:
        wce = response['writeConcernError']
        raise WriteConcernError(wce['errmsg'], wce['code'], wce)

    if not response["ok"]:

        details = response
        # Mongos returns the error details in a 'raw' object
        # for some errors.
        if "raw" in response:
            for shard in itervalues(response["raw"]):
                # Grab the first non-empty raw error from a shard.
                if shard.get("errmsg") and not shard.get("ok"):
                    details = shard
                    break

        errmsg = details["errmsg"]
        if allowable_errors is None or errmsg not in allowable_errors:

            # Server is "not master" or "recovering"
            if (errmsg.startswith("not master")
                    or errmsg.startswith("node is recovering")):
                raise NotMasterError(errmsg, response)

            # Server assertion failures
            if errmsg == "db assertion failure":
                errmsg = ("db assertion failure, assertion: '%s'" %
                          details.get("assertion", ""))
                raise OperationFailure(errmsg,
                                       details.get("assertionCode"),
                                       response)

            # Other errors
            code = details.get("code")
            # findAndModify with upsert can raise duplicate key error
            if code in (11000, 11001, 12582):
                raise DuplicateKeyError(errmsg, code, response)
            elif code == 50:
                raise ExecutionTimeout(errmsg, code, response)
            elif code == 43:
                raise CursorNotFound(errmsg, code, response)

            msg = msg or "%s"
            raise OperationFailure(msg % errmsg, code, response)