"Session bug" (#19914) is back: add other errors when you find them.

Hi, everyone:

The session bug[1] is back. This means when folks edit a page, and then
click "save page" to submit the changes, they'll get the following error:

     "Sorry! We could not process your edit due to a loss of session data.
Please try again. If it still does not work, try logging out and logging
back in."

Some other folks have mentioned experiencing different errors. If you have
any other problems with logging in, out, or staying logged in, would you
kindly update the bug with the specific steps it takes to reproduce that
error?

Let's get this little guy nailed down!

J

[1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=19914

----------------------------
julee@adobe.com
@adobejulee