make gstlal an optional import in the postscript
make gstlal an optional import in the postscript, so that the summary plots without pastro calculation(for gstlal) are produced if the env doesn't have gstlal.
make gstlal an optional import in the postscript, so that the summary plots without pastro calculation(for gstlal) are produced if the env doesn't have gstlal.