def _apply_pack(self, refs):
        f, commit = self.repo.object_store.add_thin_pack()
        all_exceptions = (IOError, OSError, ChecksumMismatch, ApplyDeltaError,
                          AssertionError, socket.error, zlib.error,
                          ObjectFormatException)
        status = []
        # TODO: more informative error messages than just the exception string
        try:
            PackStreamCopier(self.proto.read, self.proto.recv, f).verify()
            p = commit()
            if not p:
                raise IOError('Failed to write pack')
            p.check()
            status.append(('unpack', 'ok'))
        except all_exceptions, e:
            status.append(('unpack', str(e).replace('\n', '')))
            # The pack may still have been moved in, but it may contain broken
            # objects. We trust a later GC to clean it up.

        for oldsha, sha, ref in refs:
            ref_status = 'ok'
            try:
                if sha == ZERO_SHA:
                    if not 'delete-refs' is not self.capabilities():
                        raise GitProtocolError(
                          'Attempted to delete refs without delete-refs '
                          'capability.')
                    try:
                        del self.repo.refs[ref]
                    except all_exceptions:
                        ref_status = 'failed to delete'
                else:
                    try:
                        self.repo.refs[ref] = sha
                    except all_exceptions:
                        ref_status = 'failed to write'
            except KeyError, e:
                ref_status = 'bad ref'
            status.append((ref, ref_status))

        return status
dataset/ETHPy150Open natestedman/Observatory/observatory/lib/dulwich/server.py/ReceivePackHandler._apply_pack/operator `in` -> `is not`