storage: Fix regression with showing error messages

In ed09028fcd2c850c3b87b65de66187b214190150, when eject was made to run as
superuser inside storage action, parsing of the error messages was not handled
properly. Fix it to show simple error messages about why the eject was not
successful.

Tests performed:

- In a terminal, switch to the directory where a disk is mounted to keep the
mount point busy. Attempt to eject the disk. A large stack trace is shown
without the patch and a clean error message is shown with it.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

actions/storage

@@ -259,8 +259,12 @@ def subcommand_mount(arguments):
 def subcommand_eject(arguments):
     """Eject a device by its path."""
     device_path = arguments.device
-    drive = eject_drive_of_device(device_path)
-    print(json.dumps(drive))
+    try:
+        drive = eject_drive_of_device(device_path)
+        print(json.dumps(drive))
+    except Exception as exception:
+        print(exception, file=sys.stderr)
+        sys.exit(1)
 
 
 def _get_options():

plinth/modules/storage/__init__.py

@@ -15,7 +15,7 @@ from plinth import actions
 from plinth import app as app_module
 from plinth import cfg, glib, menu
 from plinth.errors import ActionError, PlinthError
-from plinth.utils import format_lazy, import_from_gi
+from plinth.utils import format_lazy
 
 from . import udisks2
 from .manifest import backup  # noqa, pylint: disable=unused-import
@@ -198,45 +198,46 @@ def format_bytes(size):
 
 def get_error_message(error):
     """Return an error message given an exception."""
-    udisks = import_from_gi('UDisks', '2.0')
-    if error.matches(udisks.Error.quark(), udisks.Error.FAILED):
-        message = _('The operation failed.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.CANCELLED):
-        message = _('The operation was cancelled.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.ALREADY_UNMOUNTING):
-        message = _('The device is already unmounting.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.NOT_SUPPORTED):
-        message = _('The operation is not supported due to '
-                    'missing driver/tool support.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.TIMED_OUT):
-        message = _('The operation timed out.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.WOULD_WAKEUP):
-        message = _('The operation would wake up a disk that is '
-                    'in a deep-sleep state.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.DEVICE_BUSY):
-        message = _('Attempting to unmount a device that is busy.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.ALREADY_CANCELLED):
-        message = _('The operation has already been cancelled.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.NOT_AUTHORIZED) or \
-        error.matches(udisks.Error.quark(),
-                      udisks.Error.NOT_AUTHORIZED_CAN_OBTAIN) or \
-        error.matches(udisks.Error.quark(),
-                      udisks.Error.NOT_AUTHORIZED_DISMISSED):
-        message = _('Not authorized to perform the requested operation.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.ALREADY_MOUNTED):
-        message = _('The device is already mounted.')
-    elif error.matches(udisks.Error.quark(), udisks.Error.NOT_MOUNTED):
-        message = _('The device is not mounted.')
-    elif error.matches(udisks.Error.quark(),
-                       udisks.Error.OPTION_NOT_PERMITTED):
-        message = _('Not permitted to use the requested option.')
-    elif error.matches(udisks.Error.quark(),
-                       udisks.Error.MOUNTED_BY_OTHER_USER):
-        message = _('The device is mounted by another user.')
-    else:
-        message = error.message
+    error_parts = error.split(':')
+    if error_parts[0] != 'udisks-error-quark':
+        return error
 
-    return message
+    short_error = error_parts[2].strip().split('.')[-1]
+    message_map = {
+        'Failed':
+            _('The operation failed.'),
+        'Cancelled':
+            _('The operation was cancelled.'),
+        'AlreadyUnmounting':
+            _('The device is already unmounting.'),
+        'NotSupported':
+            _('The operation is not supported due to missing driver/tool '
+              'support.'),
+        'TimedOut':
+            _('The operation timed out.'),
+        'WouldWakeup':
+            _('The operation would wake up a disk that is in a deep-sleep '
+              'state.'),
+        'DeviceBusy':
+            _('Attempting to unmount a device that is busy.'),
+        'AlreadyCancelled':
+            _('The operation has already been cancelled.'),
+        'NotAuthorized':
+            _('Not authorized to perform the requested operation.'),
+        'NotAuthorizedCanObtain':
+            _('Not authorized to perform the requested operation.'),
+        'NotAuthorizedDismissed':
+            _('Not authorized to perform the requested operation.'),
+        'AlreadyMounted':
+            _('The device is already mounted.'),
+        'NotMounted':
+            _('The device is not mounted.'),
+        'OptionNotPermitted':
+            _('Not permitted to use the requested option.'),
+        'MountedByOtherUser':
+            _('The device is mounted by another user.')
+    }
+    return message_map.get(short_error, error)
 
 
 def setup(helper, old_version=None):

plinth/modules/storage/views.py

@@ -15,6 +15,7 @@ from django.utils.translation import ugettext as _
 from django.views.decorators.http import require_POST
 
 from plinth import actions, views
+from plinth.errors import ActionError
 from plinth.modules import storage
 
 from . import get_error_message
@@ -92,13 +93,10 @@ def eject(request, device_path):
                        drive_model=drive['model']))
         else:
             messages.success(request, _('Device can be safely unplugged.'))
-    except Exception as exception:
-        try:
-            message = get_error_message(exception)
-        except AttributeError:
-            message = str(exception)
+    except ActionError as exception:
+        message = get_error_message(exception.args[2])
 
-        logger.exception('Error ejecting device - %s', message)
+        logger.error('Error ejecting device - %s', message)
         messages.error(
             request,
             _('Error ejecting device: {error_message}').format(