Hi,

This is the first issue I submit so please correct me if I do anything wrong. 

Description of the issue:
imporlib logs 'wrote <path to .pyc file>' even when file creation fails with OSError (for lack of write persmission for example) 

Reproducing the bug in Python 3.6 on ubuntu 16.04:

cd /home/quentin/tmp
mkdir __pycache__
chmod -R -w __pycache__
echo '1 + 1' > spam.py
python -vv -c'import spam' 2>&1 | grep '__pycache__/spam'

Output:
# could not create '/home/quentin/tmp/__pycache__/spam.cpython-36.pyc': PermissionError(13, 'Permission denied')
# wrote '/home/quentin/tmp/__pycache__/spam.cpython-36.pyc'


Reason:
SourceFileLoader.set_data() silences OSError raised by _write_atomic (importlib/_bootstrap_external.py line 875) 
Then SourceLoader.get_code() does not see that something went awry and logs file creation (same file, line 789) 


If it is worth fixing I would be glad to contribute a patch, but would probably need a little guidance.

New changeset 9e14e49f13ef1a726f31efe6689285463332db6e by Miss Islington (bot) (Quentin Agren) in branch 'master':
bpo-35024: Remove redundant and possibly incorrect verbose message after writing '.pyc' (GH-9998)
https://github.com/python/cpython/commit/9e14e49f13ef1a726f31efe6689285463332db6e