Fix microsoft#1148: ModuleNotFoundError: No module named 'debugpy'

Fix microsoft#1149: UserWarning: incompatible copy of pydevd already imported

Fix formatting for sys.path entry passed to subprocesses.

src/debugpy/_vendored/force_pydevd.py

@@ -67,7 +67,7 @@ def debugpy_breakpointhook():
 
 # This is important when pydevd attaches automatically to a subprocess. In this case, we have to
 # make sure that debugpy is properly put back in the game for users to be able to use it.
-pydevd_defaults.PydevdCustomization.PREIMPORT = '%r;%s' % (
+pydevd_defaults.PydevdCustomization.PREIMPORT = '%s;%s' % (
     os.path.dirname(os.path.dirname(debugpy.__file__)), 
     'debugpy._vendored.force_pydevd'
 )