tests: verify-bson shouldn't error out on old pymongo.
tests: verify-bson shouldn't error out on old pymongo.

Although we skip tests when the pymongo installed is too old, there
was a case where we still errored out with a backtrace.

As a workaround, when an insufficient pymongo is found, create a dummy
Binary class, to avoid the error later on.

algernon/libmongo-client,algernon/libmongo-client,algernon/libmongo-client