[devel at bb.net] Adding attribute to serialized objects

[Maria Marcano]

Hi,

Do you know how we should handle adding an attribute to serialized object.

We are doing some customizations and we would like to add content_type to
class HTMLLogFile(styles.Versioned, LogFile):

so we increased the

persistenceVersion = 2
and added the

def upgradeToVersion2(self):
self.content_type = ''
self.wasUpgraded = True

But we got an error if we want to run buildbot on a different branch that
uses persistenceVersion = 1

the exception is thrown from this library
twisted/persisted/styles.py:400 in versionUpgrade
assert persistVers <=  currentVers, "Sorry, can't go backwards in time."

Do you know how this should be handled?, it looks like we are missing/not
handle something?

Thanks!
Maria
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