device: move device-related code into a separate package

trezor_agent/device/__init__.py

@@ -0,0 +1,28 @@
+"""Cryptographic hardware device management."""
+
+import logging
+
+from . import trezor
+from . import keepkey
+from . import ledger
+from . import interface
+
+log = logging.getLogger(__name__)
+
+DEVICE_TYPES = [
+    trezor.Trezor,
+    keepkey.KeepKey,
+    ledger.LedgerNanoS,
+]
+
+
+def detect(identity_str, curve_name):
+    """Detect the first available device and return it to the user."""
+    for device_type in DEVICE_TYPES:
+        try:
+            with device_type(identity_str, curve_name) as d:
+                return d
+        except interface.NotFoundError as e:
+            log.debug('device not found: %s', e)
+    raise IOError('No device found: "{}" ({})'.format(identity_str,
+                                                      curve_name))