Raise exception for ddp_cpu not supported for TPUs

[kaushikb11]

What does this PR do?

Fixes #7810

Does your PR introduce any breaking changes? If yes, please list them.

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[codecov]

Codecov Report

Merging #8530 (6a9a485) into master (52526c2) will decrease coverage by 4%.
The diff coverage is 50%.

@@           Coverage Diff           @@
##           master   #8530    +/-   ##
=======================================
- Coverage      92%     88%    -4%     
=======================================
  Files         218     218            
  Lines       14404   14406     +2     
=======================================
- Hits        13297   12703   -594     
- Misses       1107    1703   +596     

[Borda]

@kaushikb11 still draft?

[tchaton]

LGTM ! Thanks for checking that

[pep8speaks]

Hello @kaushikb11! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2021-07-26 10:06:24 UTC