Remove unused _KeyStrength imports

buildstream/_artifactcache/ostreecache.py

@@ -26,7 +26,6 @@ import tempfile
 
 from .. import _ostree, _signals, utils
 from .._exceptions import ArtifactError
-from ..element import _KeyStrength
 from .._ostree import OSTreeError
 
 from . import ArtifactCache

buildstream/_artifactcache/tarcache.py

@@ -24,7 +24,6 @@ import tarfile
 import subprocess
 
 from .. import utils, ProgramNotFoundError
-from ..element import _KeyStrength
 from .._exceptions import ArtifactError
 
 from . import ArtifactCache

buildstream/_scheduler/pullqueue.py

@@ -19,9 +19,6 @@
 #        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
 #        Jürg Billeter <juerg.billeter@codethink.co.uk>
 
-# BuildStream toplevel imports
-from ..element import _KeyStrength
-
 # Local imports
 from . import Queue, QueueStatus, QueueType