The message thread https://sourceforge.net/p/roundup/mailman/roundup-users/thread/0685ed03-89a1-5278-f3e7-a01a9d082576%40cendio.se/#msg37382615

with subject: Upgrading from 1.4.20 to 2.0 gives error with values stored as long in 
database

is due to a bug in some versions of roundup before 1.2.0. The bug doesn't occur in
version 1.2.0 (10/206), but that may not be the version with the fix. It was just
the earliest roundup version I could run under python 2.7.

The params tuple in the history is represented as:

  ("issue", 5432L, "status)

where the ID (second field) is a long int. In newer versions this is represented as:

  ("issue", "5432", "status)

In python3 5432L is not a valid integer value (in python2 it is a Long int).
Eval'ing the tuple representation thus throws a SyntaxError in python3.