Added new construct :class:`.api.CantDeserializeException` which can be
raised by user-defined deserializer functions which would be passed to
:paramref:`.CacheRegion.deserializer`, to indicate a cache value that can't
be deserialized and therefore should be regenerated. This can allow an
application that's been updated to gracefully re-cache old items that were
persisted from a previous version of the application. Pull request courtesy
Simon Hewitt.

Closes: #236
Pull-request: https://github.com/sqlalchemy/dogpile.cache/pull/236
Pull-request-sha: f2ec26521acb8069d092c51749952f8540b5d75c

Change-Id: Idec175b9c06274628d3d027024f9878abb1d188b

Change-Id: I97e477796cd3d747270d0b5c2bfd34ada7e63794

Change-Id: Ic9de2099134e8bd9c20a802ff604599ef511cfd9

Moved the :paramref:`.MemcacheArgs.dead_retry` argument and the
:paramref:`.MemcacheArgs.socket_timeout` argument which were
erroneously added to the "set_parameters",
where they have no effect, to be part of the Memcached connection
arguments :paramref:`.MemcachedBackend.dead_retry`,
:paramref:`.MemcachedBackend.socket_timeout`.

Indeed, In my previous patch [1] I proposed to add the ``dead_retry`` and ``socket_timeout`` params to the ``MemcacheArgs`` class. I was wrong. My goal was to pass these parameters to the client during its initialization to set the memcached client dead_retry and socket_timeout arguments [2].

By using the MemcacheArgs they are passed to the method calls which is not what it was requested in the feature request [3]. I misunderstood the goal of this class (MemcacheArgs).

The ``MemcacheArgs`` class is only inherited by the ``MemcachedBackend`` class and the ``PylibmcBackend`` class. Both libraries doesn't support ``dead_retry`` and ``socket_timeout`` in their methods related to the memcache API commands (set, get, set_multi, etc), so for this reason I think we can move those parameters safely.

My previous patch led to issues [4][5] that I'm able to reproduce locally by using oslo.cache's functional test. These changes fix these issues.

[1] https://github.com/sqlalchemy/dogpile.cache/commit/1de93aab14c1274f20c1f44f8adff3b143c864f6
[2] https://github.com/linsomniac/python-memcached/blob/7942465eba2009927e5d14b4b6dbd48b75780d80/memcache.py#L165
[3] https://github.com/sqlalchemy/dogpile.cache/issues/223
[4] https://bugzilla.redhat.com/show_bug.cgi?id=2103117
[5] https://review.opendev.org/c/openstack/requirements/+/848827

Closes: #228
Pull-request: https://github.com/sqlalchemy/dogpile.cache/pull/228
Pull-request-sha: dcef04b200c62d615054b3520ece480825597e61

Change-Id: Ic77c1d657b81449a34114cf9f61c350ffc7e2ba1