diff --git a/radicale/acl/IMAP.py b/radicale/acl/IMAP.py
index e944f4d..dd50111 100644
--- a/radicale/acl/IMAP.py
+++ b/radicale/acl/IMAP.py
@@ -2,8 +2,6 @@
 #
 # This file is part of Radicale Server - Calendar Server
 # Copyright © 2012 Daniel Aleksandersen
-# Copyright © 2011 Corentin Le Bail
-# Copyright © 2011 Guillaume Ayoub
 #
 # This library is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -39,45 +37,53 @@ from radicale import acl, config, log
 IMAP_SERVER = config.get("acl", "imap_auth_host_name")
 IMAP_SERVER_PORT = config.get("acl", "imap_auth_host_port")
 
+
 def has_right(owner, user, password):
     """Check if ``user``/``password`` couple is valid."""
-
     if not user or (owner not in acl.PRIVATE_USERS and user != owner):
         # No user given, or owner is not private and is not user, forbidden
         return False
 
-    log.LOGGER.debug("[IMAP ACL] Connecting to %s:%s." % (IMAP_SERVER, IMAP_SERVER_PORT,))
+    log.LOGGER.debug(
+        "[IMAP ACL] Connecting to %s:%s." % (IMAP_SERVER, IMAP_SERVER_PORT,))
     connection = imaplib.IMAP4(host=IMAP_SERVER, port=IMAP_SERVER_PORT)
 
-    def secure_connection():
-        try:
-            connection.starttls()
-            log.LOGGER.debug("[IMAP ACL] Server connection changed to TLS.")
-            return True
-        except (IMAP4.error, IAMP4.abort) as err:
-            import sys
-            PY_MIN = float(3.2)
-            PY_SYS = float("%s.%s" % (sys.version_info.major, sys.version_info.minor))
-            if PY_SYS < PY_MIN:
-                log.LOGGER.error("[IMAP ACL] Python 3.2 or newer is required for TLS.")
-            log.LOGGER.warning("[IMAP ACL] Server at %s failed to accept TLS connection because of: %s" % (IMAP_SERVER, str(err)))
-        return False # server is not secure
+    server_is_local = (IMAP_SERVER == "localhost")
 
-    def server_is_local():
-        if IMAP_HOST == "localhost":
-            log.LOGGER.warning("[IMAP ACL] Server is local. Will allow transmitting unencrypted credentials.")
-            return True
-        return False # server is not local
+    connection_is_secure = False
+    try:
+        connection.starttls()
+        log.LOGGER.debug("[IMAP ACL] Server connection changed to TLS.")
+        connection_is_secure = True
+    except AttributeError:
+        if not server_is_local:
+            log.LOGGER.error(
+                "[IMAP ACL] Python 3.2 or newer is required for TLS.")
+    except (imaplib.IMAP4.error, imaplib.IMAP4.abort) as exception:
+        log.LOGGER.warning(
+            "[IMAP ACL] Server at %s failed to accept TLS connection "
+            "because of: %s" % (IMAP_SERVER, exception))
 
-    """Enforcing security policy of only transmitting credentials over TLS or to local server."""
-    if secure_connection() or server_is_local():
+    if server_is_local and not connection_is_secure:
+        log.LOGGER.warning(
+            "[IMAP ACL] Server is local. "
+            "Will allow transmitting unencrypted credentials.")
+
+    if connection_is_secure or server_is_local:
         try:
-            connection.login( user, password )
+            connection.login(user, password)
             connection.logout()
-            log.LOGGER.debug("[IMAP ACL] Authenticated user %s via %s." % (user, IMAP_SERVER))
+            log.LOGGER.debug(
+                "[IMAP ACL] Authenticated user %s "
+                "via %s." % (user, IMAP_SERVER))
             return True
-        except ( imaplib.IMAP4.error, imaplib.IMAP4.abort, Exception ) as err:
-            log.LOGGER.error("[IMAP ACL] Server could not authenticate user %s because of: %s" % (user, str(err)))
+        except (imaplib.IMAP4.error, imaplib.IMAP4.abort) as exception:
+            log.LOGGER.error(
+                "[IMAP ACL] Server could not authenticate user %s "
+                "because of: %s" % (user, exception))
     else:
-        log.LOGGER.critical("[IMAP ACL] Server did not support TLS and is not ``localhost``. Refusing to transmit passwords under these conditions. Authentication attempt aborted.")
-    return False # authentication failed
+        log.LOGGER.critical(
+            "[IMAP ACL] Server did not support TLS and is not ``localhost``. "
+            "Refusing to transmit passwords under these conditions. "
+            "Authentication attempt aborted.")
+    return False  # authentication failed