Make online detection a bit smarter (bug 1730)

If we don't have "ifconfig" and "ip" assume we're online
(because we can't determine that we're offline), and if
detecting the network connection fails for some reason,
also assume that we're online. This avoid bogus "you're
offline" messages while still giving good feedback to
users who try to check for new episodes while offline.

src/gpodder/util.py

@@ -1706,15 +1706,21 @@ def connection_available():
         elif gpodder.ui.osx:
             return len(list(osx_get_active_interfaces())) > 0
         else:
-            if len(list(unix_get_active_interfaces())) > 0:
+            if (find_command('ifconfig') is not None and
+                    len(list(unix_get_active_interfaces())) > 0):
                 return True
-            elif len(list(linux_get_active_interfaces())) > 0:
+            elif (find_command('ip') is not None and
+                    len(list(linux_get_active_interfaces())) > 0):
+                return True
+            else:
+                # If we have neither "ifconfig" nor "ip", assume we're online (bug 1730)
                 return True
 
         return False
     except Exception, e:
         logger.warn('Cannot get connection status: %s', e, exc_info=True)
-        return False
+        # When we can't determine the connection status, act as if we're online (bug 1730)
+        return True
 
 
 def website_reachable(url):