address comments from @akshayc11

tools/extras/install_mmseg.sh

@@ -62,21 +62,21 @@ python setup.py install --prefix `pwd`
 ## so that should be pretty reliable) and then we work out the location of
 ## the site-packages directory (typically it would be one level up from
 ## the location of the mmseg.py file but using find seems more reliable
-mmseg_file_lib=$(find ./mmseg-1.3.0/lib/ -type f -name mmseg.py | head -n 1)
-mmseg_file_lib64=$(find ./mmseg-1.3.0/lib64/ -type f -name mmseg.py | head -n 1)
-if [ -f $mmseg_file_lib ]; then
+mmseg_file_lib=$(find ./mmseg-1.3.0/lib/ -type f -name mmseg.py | head -n1)
+mmseg_file_lib64=$(find ./mmseg-1.3.0/lib64/ -type f -name mmseg.py | head -n1)
+if [ ! -z ${mmseg_file_lib+x} ]; then
   lib_dir=./lib/
-elif [ -f $mmseg_file_lib64 ]; then
+elif [ ! -z ${mmseg_file_lib64+x} ]; then
   lib_dir=./lib64/
 else
   echo >&2 "$0: ERROR: Didn't find ./mmseg-1.3.0/lib/ or ./mmseg-1.3.0/lib64/"
-  echo >&2 "  Perhaps your python or system installs python into a different dir?"
-  echo >&2 "  or some other unknown issues arised - review the script output"
-  echo >&2 "  and try to figure out what went wrong."
+  echo >&2 "  Perhaps your python or system installs python modules into"
+  echo >&2 "  a different dir or some other unknown issues arised. Review the output"
+  echo >&2 "  of the script and try to figure out what went wrong."
   exit 1
 fi
 
-site_packages_dir=$(cd ./mmseg-1.3.0; find $libdir -name "site-packages" -type d | head -n1)
+site_packages_dir=$(cd ./mmseg-1.3.0; find $lib_dir -name "site-packages" -type d | head -n1)
 (
   echo "export MMSEG=\"$PWD/mmseg-1.3.0\""
   echo "export PYTHONPATH=\"\${PYTHONPATH:-}:\$MMSEG/${site_packages_dir}\""