Colons in notebook name causes notebook deletion without warning

[ghost]

If you change the name of a notebook by clicking on the notebook title in the browser, and the new name includes a colon, the notebook is "saved" without objection, while in the background the ipynb file is wiped -- the filename is truncated at the colon and the file is empty. This is not apparent in the browser until you close the notebook. This is on Windows.

I discovered this by successively changing the names of a set of 5 notebooks to include colons, and continued to make changes to the notebooks, saving, etc. Then I closed them and later went to re-open them to discover everything was gone. There was never any warning at all while in the browser. Given that there is no warning that the notebook title == filename and colons are a fairly common character, this strikes me as a pretty serious issue!

[bfroehle]

The easiest way to fix this might be to add a list of reserved characters to notebook_name_blacklist_re and a corresponding note in the save widget.

Note that this bug does not impact my linux installation.