Attempt to move room aliases on room upgrades

[richvdh]

Builds on #4091

[erikjohnston]

I'd probably avoid using else clause for statements that we know aren't going to raise an exception. I can never really remember if the else means "if there was no exception" or "if there was an exception that we didn't catch" or whatever.

[Guerteltier]

else is "if there was no exception"
https://docs.python.org/3/tutorial/errors.html

The try … except statement has an optional else clause, which, when present, must follow all except clauses. It is useful for code that must be executed if the try clause does not raise an exception. For example:

for arg in sys.argv[1:]:
    try:
        f = open(arg, 'r')
    except OSError:
        print('cannot open', arg)
    else:
        print(arg, 'has', len(f.readlines()), 'lines')
        f.close()

The use of the else clause is better than adding additional code to the try clause because it avoids accidentally catching an exception that wasn’t raised by the code being protected by the try … except statement.

[richvdh]

(this is also now failing due to #4099 landing)