Superset chart incorrectly throwing error Virtual dataset query must be read-only

A chart built off of a virtual datasource is erroring saying that the virtual datasource must be readonly but the query is only a select query (it is not modifying any table). It does contain WITH statements, and removing the WITH statements doesn’t result in the error. It seems like queries with WITH statements are getting miscategorized as “Readonly”.

Result: Error thrown: Virtual dataset query must be read-only

Expected Result: Chart should load

Looks like regression caused by https://github.com/apache/incubator-superset/pull/11236#issuecomment-710669738

Environment

(please complete the following information):

• superset version: master

Checklist

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if there are any.
• I have reproduced the issue with at least the latest released version of superset.
• I have checked the issue tracker for the same issue and I haven’t found one similar.

[mistercrunch]

For reference, I think this is where the lack of magic happens: https://github.com/andialbrecht/sqlparse/blob/master/sqlparse/sql.py#L425-L436

[serenajiang]

fixed in #11365