You may want to open file "packages/SideBarGit/SideBarGit.py"
And replace "debug = False" to "debug = True" and paste the output of everything about git here.
Also that problem is an OS problem, I'm not sure If I can help you. You may don't have access to the file, or the python can't access the file or git can't access, don't know.
Try with the same file on command line.
Try on sublime console
os.path.exists('/your file name here/')