ImportError: druggability package was not found

[accibio]

Hi,
I am trying to run the Calculate Grids module of DruGUI in VMD. After loading the PSF, PDB and DCD files, when I run it, few .dx and .dcd files are generated but an Application Error popup window appears midway while writing the prot_positive.dx file along with this message:

Traceback (most recent call last):
File "/home/DruGUI/Calculate_Grids/prot.py", line 21, in
'to proceed with calculation'.format(file))
ImportError: druggability package was not found. Edit /home/DruGUI/Calculate_Grids/prot.py to proceed with calculation
Traceback (most recent call last):
File "/home/DruGUI/Calculate_Grids/prot.py", line 21, in
'to proceed with calculation'.format(file))
ImportError: druggability package was not found. Edit /home/DruGUI/Calculate_Grids/prot.py to proceed with calculation
while executing
"exec $pythonexe [file join "$outputdir" "$pyprefix.py"] critical"
(procedure "::druggability::Assess_druggability" line 20)
invoked from within
"::druggability::Assess_druggability"
(procedure "::druggability::Process_system" line 218)
invoked from within
"::druggability::Process_system"
invoked from within
".druggui.main_frame.process.button invoke"
("uplevel" body line 1)
invoked from within
"uplevel #0 [list $w invoke]"
(procedure "tk::ButtonUp" line 22)
invoked from within
"tk::ButtonUp .druggui.main_frame.process.button"
(command bound to event)

I am using Python2.7. Similar issue was posted here #180 but the solution is not clear to me. Please help.
Thanks!