Add custom exception to assignment mode and backup

For: QubesOS#645

Author: ben-grande

qubes/api/admin.py

@@ -1813,7 +1813,7 @@ 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)
 
@@ -2096,9 +2096,7 @@ async def backup_execute(self):
             qubes.config.backup_profile_dir, self.arg + ".conf"
         )
         if not os.path.exists(profile_path):
-            raise qubes.exc.ProtocolError(
-                "Backup profile does not exist: {}".format(self.arg)
-            )
+            raise qubes.exc.QubesBackupProfileNotFoundError(profile=self.arg)
 
         if not hasattr(self.app, "api_admin_running_backups"):
             self.app.api_admin_running_backups = {}
@@ -2117,7 +2115,7 @@ 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]
 
@@ -2159,9 +2157,7 @@ async def backup_info(self):
             qubes.config.backup_profile_dir, self.arg + ".conf"
         )
         if not os.path.exists(profile_path):
-            raise qubes.exc.ProtocolError(
-                "Backup profile does not exist: {}".format(self.arg)
-            )
+            raise qubes.exc.QubesBackupProfileNotFoundError(profile=self.arg)
 
         backup = await self._load_backup_profile(self.arg, skip_passphrase=True)
         return backup.get_backup_summary()

qubes/exc.py

@@ -237,6 +237,15 @@ def __init__(self, msg=None):
         super().__init__(msg or "This feature is not available")
 
 
+class QubesBackupProfileNotFoundError(QubesException):
+    """Thrown at user when backup was manually cancelled"""
+
+    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"""
 
@@ -325,6 +334,12 @@ class DeviceAlreadyAssigned(QubesException, KeyError):
     """
 
 
+class QubesUnrecognizedDeviceAssignmentMode(ProtocolError):
+    """
+    Device assignment is not as expected.
+    """
+
+
 class UnrecognizedDevice(QubesException, ValueError):
     """
     Device identity is not as expected.