Vitess is a database clustering system for horizontal scaling of MySQL. Users can either intentionally or inadvertently create a keyspace containing `/` characters such that from that point on, anyone who tries to view keyspaces from VTAdmin will receive an error. Trying to list all the keyspaces using `vtctldclient GetKeyspaces` will also return an error. Note that all other keyspaces can still be administered using the CLI (vtctldclient). This issue is fixed in version 16.0.1. As a workaround, delete the offending keyspace using a CLI client (vtctldclient).