Rewrite DNF updates module to use DNF's Python API

This is a lot easier than trying to parse the DNF CLI output.

i3pystatus/updates/__init__.py

@@ -126,7 +126,10 @@ class Updates(Module):
         for backend in self.backends:
             name = backend.__class__.__name__
             updates, notif_body = backend.updates
-            updates_count += updates
+            try:
+                updates_count += updates
+            except TypeError:
+                pass
             self.data[name] = updates
             self.notif_body[name] = notif_body or ""
 

i3pystatus/updates/dnf.py

@@ -1,33 +1,40 @@
-from i3pystatus.core.command import run_through_shell
 from i3pystatus.updates import Backend
-from re import split, sub
+try:
+    import dnf
+    HAS_DNF_BINDINGS = True
+except ImportError:
+    HAS_DNF_BINDINGS = False
 
 
 class Dnf(Backend):
     """
-    Gets updates for RPM-based distributions with `dnf check-update`.
+    Gets updates for RPM-based distributions using the `DNF API`_
 
-    The notification body consists of the status line followed by the package
-    name and version for each update.
+    The notification body consists of the package name and version for each
+    available update.
 
-    https://dnf.readthedocs.org/en/latest/command_ref.html#check-update-command
+    .. _`DNF API`: http://dnf.readthedocs.io/en/latest/api.html
     """
 
     @property
     def updates(self):
-        command = ["dnf", "check-update"]
-        dnf = run_through_shell(command)
-        if dnf.err:
-            return "?", dnf.err
+        if HAS_DNF_BINDINGS:
+            try:
+                with dnf.Base() as base:
+                    base.read_all_repos()
+                    base.fill_sack()
+                    upgrades = base.sack.query().upgrades().run()
 
-        raw = dnf.out
-        update_count = 0
-        if dnf.rc == 100:
-            lines = raw.splitlines()[2:]
-            lines = [l for l in lines if len(split("\s+", l.rstrip())) == 3]
-            update_count = len(lines)
-        notif_body = sub(r"(\S+)\s+(\S+)\s+\S+\s*\n", r"\1: \2\n", raw)
-        return update_count, notif_body
+                notif_body = ''.join([
+                    '%s: %s-%s\n' % (pkg.name, pkg.version, pkg.release)
+                    for pkg in upgrades
+                ])
+                return len(upgrades), notif_body
+            except Exception as exc:
+                self.logger.error('DNF update check failed', exc_info=True)
+                return '?', exc.__str__()
+        else:
+            return '?', 'Failed to import DNF Python bindings'
 
 Backend = Dnf