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Beginning with 4.1.26, the eggmonster install lock mechanism (which
prevents other eggmonster instances on the same system from upgrading
packages simultaneously) was changed to be more platform friendly and
work as a context manager.
This change also tweaked the semantic meaning of the lockfile
(`/tmp/eggmonster-install-lock`). In previous versions, the lock file
was kept around, and locks were acquired by setting the EXCLUSIVE flag
on the file. Beginning with 4.1.26, the file is removed after the lock
is released. Thus when upgrading to 4.1.26, one must be careful to
remove the lockfile or subsequent package install operations will fail.