error when using --save and writing a CTE

[edublancas]

(similar to #651, let's work on that one first)

more context: create-table-bug-2.ipynb.zip

[fenrir-san]

Hey @edublancas
I checked out the file and only the last cell is still creating an error when I ran it. Please confirm if it is the same for you. The last second cell error seems to have been resolved by a previous update.

[edublancas]

if the first example has been fixed, just make sure we have a unit test for it (it might be in the test_magic.py file. And then focus on fixing the second case

[fenrir-san]

Still working on the first one
Unsure where to start
#651 brought me here so thought to check it if I can find a lead

[fenrir-san]

@edublancas Do we want to show a warning or raise a usage error if we are disabling the CTE when a saved snippet is used in the expression?

[edublancas]

we show a warning