Added prc to supported convert from formats (#2801)

Improved error message for not able to listen to ipv6 address with gevent

cps/constants.py

@@ -149,7 +149,7 @@ del env_CALIBRE_PORT
 
 EXTENSIONS_AUDIO = {'mp3', 'mp4', 'ogg', 'opus', 'wav', 'flac', 'm4a', 'm4b'}
 EXTENSIONS_CONVERT_FROM = ['pdf', 'epub', 'mobi', 'azw3', 'docx', 'rtf', 'fb2', 'lit', 'lrf',
-                           'txt', 'htmlz', 'rtf', 'odt', 'cbz', 'cbr']
+                           'txt', 'htmlz', 'rtf', 'odt', 'cbz', 'cbr', 'prc']
 EXTENSIONS_CONVERT_TO = ['pdf', 'epub', 'mobi', 'azw3', 'docx', 'rtf', 'fb2',
                          'lit', 'lrf', 'txt', 'htmlz', 'rtf', 'odt']
 EXTENSIONS_UPLOAD = {'txt', 'pdf', 'epub', 'kepub', 'mobi', 'azw', 'azw3', 'cbr', 'cbz', 'cbt', 'cb7', 'djvu', 'djv',

cps/server.py

@@ -131,7 +131,7 @@ class WebServer(object):
             sock = WSGIServer.get_listener(address, family=socket.AF_INET6)
         except socket.error as ex:
             log.error('%s', ex)
-            log.warning('Unable to listen on "", trying on IPv4 only...')
+            log.warning('Unable to listen on {}, trying on IPv4 only...'.format(address))
             address = ('', self.listen_port)
             sock = WSGIServer.get_listener(address, family=socket.AF_INET)