Such constant was missing and its value was missing from the set of requirements
that needs to be preserved through stream clone. This did not had any
consequence yet as the "bundle 2 does not filter its requirements" is shadowing
However we are now in a situation where we can fix this issue. So lets do it
With the preparation work on test, changing the streamreqs value only impact two
tests, where checking the full value seems to remains relevant.
Important note: Since older version of Mercurial used the old supportedformat
class attribute to check for stream requirement they supported, older version
will consider this requirements to prevent them from using streaming clone. Even
as they support this requirements for years. Pack for stable will be send to fix
it, but they will have to be backported to older version if needed.