Add custom exception to assignment mode and backup

For: QubesOS#645

Author: ben-grande

qubes/api/admin.py

@@ -1793,7 +1793,9 @@ async def vm_device_set_required(self, endpoint, untrusted_payload):
         try:
             mode = allowed_values[untrusted_payload]
         except KeyError:
-            raise qubes.exc.ProtocolError("Invalid assignment mode")
+            raise qubes.exc.QubesUnrecognizedDeviceAssignmentMode(
+                "Invalid assignment mode"
+            )
 
         dev = VirtualDevice.from_qarg(self.arg, devclass, self.app.domains)
 
@@ -2093,7 +2095,7 @@ async def backup_execute(self):
         try:
             await backup_task
         except asyncio.CancelledError:
-            raise qubes.exc.QubesException("Backup cancelled")
+            raise qubes.exc.BackupCancelledError()
         finally:
             del self.app.api_admin_running_backups[self.arg]
 

qubes/exc.py

@@ -244,6 +244,11 @@ def __init__(self, msg=None):
 class QubesBackupProfileNotFoundError(QubesException):
     """Requested backup profile does not exist."""
 
+    def __init__(self, msg=None, profile=None):
+        super().__init__(
+            msg or "Backup profile {!r} does not exist".format(profile)
+        )
+
 
 class BackupCancelledError(QubesException):
     """Thrown at user when backup was manually cancelled"""
@@ -333,6 +338,12 @@ class DeviceAlreadyAssigned(QubesException, KeyError):
     """
 
 
+class QubesUnrecognizedDeviceAssignmentMode(ProtocolError):
+    """
+    Device assignment is not as expected.
+    """
+
+
 class UnrecognizedDevice(QubesException, ValueError):
     """
     Device identity is not as expected.