/usr/lib/python2.7/dist-packages/grc_gnuradio/blks2/error_rate.py is in gnuradio 3.5.3.2-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/python2.7/dist-packages/grc_gnuradio/blks2/../../../../../share/pyshared/grc_gnuradio/blks2/error_rate.py