Bug? InterfaceError: Failed getting warnings when executing a query with multiple statements with get_warnings

[Barend Scholtus]

I am getting InterfaceError when I enable get_warnings and execute a query with multiple statements. I can't isolate the problem to an error in my own code so suspect a bug in the connector.

Connector version is mysql-connector-python-8.0.17 but 8.0.16 has the same issue.
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)] on win32
MySQL 5.7

To demonstrate the problem:
import mysql.connector
cnx = mysql.connector.connect(host='xx',
user='xx',
password='xx',
database='xx',
use_pure=False,
get_warnings=True)

# First test, remove later
cur = cnx.cursor()
cur.execute('SELECT "a"+1')
for row in cur:
print(row)
print(cur.fetchwarnings())
cur.close()
# End first test

# Second test
cur = cnx.cursor()
for rs in cur.execute('SELECT "a"+1; SELECT 2', multi=True):
for row in rs:
print(row)
print(rs.fetchwarnings())

For the first execute(), we execute a single statement, iterate over the cursor, fetch and print warnings. Output as expected:
(1.0,)
[('Warning', 1292, "Truncated incorrect DOUBLE value: 'a'")]

For the second test, (you can remove the first test altogether), it will execute print(row) once, then an Exception happens. Output:
(1.0,)
Traceback (most recent call last):
File "C:\Program Files\Python37\lib\site-packages\mysql\connector\connection_cext.py", line 472, in cmd_query
raw_as_string=raw_as_string)
_mysql_connector.MySQLInterfaceError: Commands out of sync; you can't run this command now

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Program Files\Python37\lib\site-packages\mysql\connector\cursor_cext.py", line 138, in _fetch_warnings
_ = self._cnx.cmd_query("SHOW WARNINGS")
File "C:\Program Files\Python37\lib\site-packages\mysql\connector\connection_cext.py", line 475, in cmd_query
sqlstate=exc.sqlstate)
mysql.connector.errors.DatabaseError: 2014 (HY000): Commands out of sync; you can't run this command now

During handling of the above exception, another exception occurred:
....etc....

Other notes:
* If you set get_warnings to False, no error happens and fetchwarnings() returns None
* If you remove the problem from the SQL code, no error happens and fetchwarnings() returns None
* use_pure can be True or False, the only difference is a slightly different traceback
* Using fetchall() instead of for row in rs gives the same result
* Many other variations give the same error.

Did anyone encounter the same problem? How did you solve it?

What am I doing wrong?