/usr/lib/python2.6/dist-packages/PyVISA-1.4.egg-info/SOURCES.txt is in pyvisa 1.4-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/python2.6/dist-packages/PyVISA-1.4.egg-info/../../../../share/pyshared/PyVISA-1.4.egg-info/SOURCES.txt