Consider this revision on the enwiki_p database:
```
>>> db = cymysql.connect(**utils.connect_info("enwiki"))
>>> db
<cymysql.connections.Connection object at 0x7fa1e1e4b890>
>>> cur = db.cursor()
>>> cur.execute("SELECT rev_comment FROM revision_userindex WHERE rev_id=295881352")
>>> list(cur)
[(b'{{logo fur\n<!-- REQUIRED -->\n|Article=Little Red Wagon Foundation\n|Use=Org\n<!-- HIGHLY RECOMMENDED -->\n|Source=http://zachtracker.com/communities/0/004/006/980/080/images/4525432850.jpg\n<!-- OVERRIDE FIELDS -->\n|Description=Logo of [[Little Red Wagon Foun',)]
```
For some reason it renders fine [[ https://en.wikipedia.org/w/index.php?title=File%3ALittle_Red_Wagon_movie_poster.jpg&oldid=570492356&diff=prev | here ]], though.
Either way, newlines should not be allowed in edit summaries.