apt_repository: Check if key already exists before trying to add it for a speed increase

library/packaging/apt_repository

@@ -335,14 +335,19 @@ class UbuntuSourcesList(SourcesList):
         line = 'deb http://ppa.launchpad.net/%s/%s/ubuntu %s main' % (ppa_owner, ppa_name, distro.codename)
         return line, ppa_owner, ppa_name
 
+    def _key_already_exists(self, key_fingerprint):
+        rc, out, err = self.module.run_command('apt-key export %s' % key_fingerprint, check_rc=True)
+        return len(err) == 0
+
     def add_source(self, line, comment='', file=None):
         if line.startswith('ppa:'):
             source, ppa_owner, ppa_name = self._expand_ppa(line)
 
             if self.add_ppa_signing_keys_callback is not None:
                 info = self._get_ppa_info(ppa_owner, ppa_name)
-                command = ['apt-key', 'adv', '--recv-keys', '--keyserver', 'hkp://keyserver.ubuntu.com:80', info['signing_key_fingerprint']]
-                self.add_ppa_signing_keys_callback(command)
+                if not self._key_already_exists(info['signing_key_fingerprint']):
+                    command = ['apt-key', 'adv', '--recv-keys', '--keyserver', 'hkp://keyserver.ubuntu.com:80', info['signing_key_fingerprint']]
+                    self.add_ppa_signing_keys_callback(command)
 
             file = file or self._suggest_filename('%s_%s' % (line, distro.codename))
         else: