torproxy: When disabling apt over tor fails, report error properly

- It is not possible to disable apt over tor for as many files as possible with
the current code because even an error in a single file will result in entire
process failing. Instead, implement a way to disable the exception.

Tests:

- Add an unparsable line into the one of the apt sources files. Disabling apt
over tor works and all file but the error file are modified.

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

plinth/modules/torproxy/privileged.py

@@ -161,12 +161,7 @@ def _enable_apt_transport_tor():
 
 def _disable_apt_transport_tor():
     """Disable package download over Tor."""
-    try:
-        aug = get_augeas()
-    except Exception:
-        # Disable what we can, so APT is not unusable.
-        pass
-
+    aug = get_augeas(raise_exception=False)
     for uri_path in iter_apt_uris(aug):
         uri = aug.get(uri_path)
         if uri.startswith(APT_TOR_PREFIX):

plinth/modules/torproxy/utils.py

@@ -36,7 +36,7 @@ def iter_apt_uris(aug):
         [aug.match(path) for path in APT_SOURCES_URI_PATHS])
 
 
-def get_augeas():
+def get_augeas(raise_exception=True):
     """Return an instance of Augeaus for processing APT configuration."""
     aug = augeas.Augeas(flags=augeas.Augeas.NO_LOAD +
                         augeas.Augeas.NO_MODL_AUTOLOAD)
@@ -51,9 +51,10 @@ def get_augeas():
     aug.load()
 
     # Check for any errors in parsing sources lists.
-    if aug.match('/augeas/files/etc/apt/sources.list/error') or \
-       aug.match('/augeas/files/etc/apt/sources.list.d//error'):
-        raise Exception('Error parsing sources list')
+    if raise_exception:
+        if aug.match('/augeas/files/etc/apt/sources.list/error') or \
+           aug.match('/augeas/files/etc/apt/sources.list.d//error'):
+            raise Exception('Error parsing sources list')
 
     return aug