Ensure data science debugger works with the shipped version of PTVSD

[DonJayamanne]

For #6907

[codecov-io]

Codecov Report

Merging #8312 into master will decrease coverage by 0.69%.
The diff coverage is 11.53%.

@@            Coverage Diff            @@
##           master    #8312     +/-   ##
=========================================
- Coverage   59.33%   58.63%   -0.7%     
=========================================
  Files         504      504             
  Lines       23096    22742    -354     
  Branches     3737     3734      -3     
=========================================
- Hits        13704    13335    -369     
- Misses       8500     8515     +15     
  Partials      892      892

Impacted Files	Coverage Δ
src/client/datascience/jupyter/jupyterDebugger.ts	10.47% <11.53%> (-0.27%)	⬇️
...nt/datascience/jupyter/invalidNotebookFileError.ts	0% <0%> (-75%)	⬇️
.../client/datascience/jupyter/jupyterConnectError.ts	0% <0%> (-66.67%)	⬇️
...science/jupyter/jupyterKernelPromiseFailedError.ts	0% <0%> (-50%)	⬇️
...ent/datascience/jupyter/jupyterWaitForIdleError.ts	0% <0%> (-50%)	⬇️
...cience/jupyter/jupyterDebuggerNotInstalledError.ts	50% <0%> (-30%)	⬇️
src/client/language/characters.ts	12% <0%> (-21.34%)	⬇️
src/client/testing/codeLenses/main.ts	60% <0%> (-17.78%)	⬇️
src/client/datascience/cellFactory.ts	72.34% <0%> (-17.32%)	⬇️
src/client/constants.ts	75% <0%> (-5%)	⬇️
... and 29 more

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[karthiknadig]

I am assuming this usage is to specifically get the path for import? i.e,

import ptvsd
ptvsd.enable_attach()

If so i think we should remember that the path extension-dir\pythonFiles\lib\python has other libraries. and by adding that path to sys.path means any import from that point on wards will look at that path first. So, parso or isort will be pulled from there. I understand the likely hood that those particular libraries being used by others is rare but something to be mindful of.