move hkdf out of util/, remove now-empty directory

setup.py

@@ -17,7 +17,7 @@ setup(name="magic-wormhole",
                 "wormhole.blocking",
                 "txwormhole",
                 "wormhole_cli",
-                "wormhole.test", "wormhole.util",
+                "wormhole.test",
                 "wormhole_server"],
       package_data={"wormhole_server": ["db-schemas/*.sql"]},
       entry_points={"console_scripts":

src/txwormhole/transcribe.py

@@ -18,7 +18,7 @@ from wormhole import __version__
 from wormhole import codes
 from wormhole.errors import ServerError, Timeout, WrongPasswordError, UsageError
 from wormhole.timing import DebugTiming
-from wormhole.util.hkdf import HKDF
+from wormhole.hkdf import HKDF
 from wormhole.channel_monitor import monitor
 
 CONFMSG_NONCE_LENGTH = 128//8

src/txwormhole/transit.py

@@ -8,7 +8,7 @@ from twisted.internet import (reactor, interfaces, defer, protocol,
 from twisted.internet.defer import inlineCallbacks, returnValue
 from twisted.protocols import policies
 from nacl.secret import SecretBox
-from wormhole.util.hkdf import HKDF
+from wormhole.hkdf import HKDF
 from wormhole.errors import UsageError
 from wormhole.timing import DebugTiming
 from . import ipaddrs

src/wormhole/blocking/transcribe.py

@@ -11,7 +11,7 @@ from .. import __version__
 from .. import codes
 from ..errors import ServerError, Timeout, WrongPasswordError, UsageError
 from ..timing import DebugTiming
-from ..util.hkdf import HKDF
+from ..hkdf import HKDF
 from ..channel_monitor import monitor
 
 SECOND = 1