diff --git a/radicale/__main__.py b/radicale/__main__.py
index 323b57f..e2ed260 100644
--- a/radicale/__main__.py
+++ b/radicale/__main__.py
@@ -28,6 +28,7 @@ import contextlib
 import os
 import signal
 import socket
+import sys
 
 from radicale import VERSION, config, log, server, storage
 from radicale.log import logger
@@ -113,7 +114,7 @@ def run():
             configuration.update(arguments_config, "arguments")
     except Exception as e:
         logger.fatal("Invalid configuration: %s", e, exc_info=True)
-        exit(1)
+        sys.exit(1)
 
     # Configure logging
     log.set_level(configuration.get("logging", "level"))
@@ -128,11 +129,11 @@ def run():
             with storage_.acquire_lock("r"):
                 if not storage_.verify():
                     logger.fatal("Storage verifcation failed")
-                    exit(1)
+                    sys.exit(1)
         except Exception as e:
             logger.fatal("An exception occurred during storage verification: "
                          "%s", e, exc_info=True)
-            exit(1)
+            sys.exit(1)
         return
 
     # Create a socket pair to notify the server of program shutdown
@@ -149,7 +150,7 @@ def run():
     except Exception as e:
         logger.fatal("An exception occurred during server startup: %s", e,
                      exc_info=True)
-        exit(1)
+        sys.exit(1)
 
 
 if __name__ == "__main__":
diff --git a/radicale/item/filter.py b/radicale/item/filter.py
index 4c46dff..2d1d179 100644
--- a/radicale/item/filter.py
+++ b/radicale/item/filter.py
@@ -450,8 +450,7 @@ def text_match(vobject_item, filter_, child_name, ns, attrib_name=None):
         condition = any(match(child.value) for child in children)
     if filter_.get("negate-condition") == "yes":
         return not condition
-    else:
-        return condition
+    return condition
 
 
 def param_filter_match(vobject_item, filter_, parent_name, ns):
@@ -467,10 +466,9 @@ def param_filter_match(vobject_item, filter_, parent_name, ns):
         if filter_[0].tag == xmlutils.make_clark("%s:text-match" % ns):
             return condition and text_match(
                 vobject_item, filter_[0], parent_name, ns, name)
-        elif filter_[0].tag == xmlutils.make_clark("%s:is-not-defined" % ns):
+        if filter_[0].tag == xmlutils.make_clark("%s:is-not-defined" % ns):
             return not condition
-    else:
-        return condition
+    return condition
 
 
 def simplify_prefilters(filters, collection_tag="VCALENDAR"):
diff --git a/radicale/rights/from_file.py b/radicale/rights/from_file.py
index 4dffb8a..9548112 100644
--- a/radicale/rights/from_file.py
+++ b/radicale/rights/from_file.py
@@ -77,9 +77,8 @@ class Rights(rights.BaseRights):
                              collection_pattern, section)
                 return rights.intersect_permissions(
                     permissions, rights_config.get(section, "permissions"))
-            else:
-                logger.debug("Rule %r:%r doesn't match %r:%r from section %r",
-                             user, sane_path, user_pattern,
-                             collection_pattern, section)
+            logger.debug("Rule %r:%r doesn't match %r:%r from section %r",
+                         user, sane_path, user_pattern, collection_pattern,
+                         section)
         logger.info("Rights: %r:%r doesn't match any section", user, sane_path)
         return ""
diff --git a/radicale/storage/__init__.py b/radicale/storage/__init__.py
index 2437834..b957451 100644
--- a/radicale/storage/__init__.py
+++ b/radicale/storage/__init__.py
@@ -240,7 +240,7 @@ class BaseCollection:
             return (template[:template_insert_pos] +
                     vtimezones + components +
                     template[template_insert_pos:])
-        elif self.get_meta("tag") == "VADDRESSBOOK":
+        if self.get_meta("tag") == "VADDRESSBOOK":
             return "".join((item.serialize() for item in self.get_all()))
         return ""
 
diff --git a/radicale/storage/multifilesystem/cache.py b/radicale/storage/multifilesystem/cache.py
index e1a087c..c143a71 100644
--- a/radicale/storage/multifilesystem/cache.py
+++ b/radicale/storage/multifilesystem/cache.py
@@ -53,7 +53,8 @@ class CollectionCacheMixin:
         if modified:
             self._storage._sync_directory(folder)
 
-    def _item_cache_hash(self, raw_text):
+    @staticmethod
+    def _item_cache_hash(raw_text):
         _hash = sha256()
         _hash.update(storage.CACHE_VERSION)
         _hash.update(raw_text)
diff --git a/radicale/tests/test_auth.py b/radicale/tests/test_auth.py
index 635ab5e..7faad0d 100644
--- a/radicale/tests/test_auth.py
+++ b/radicale/tests/test_auth.py
@@ -84,10 +84,9 @@ class TestBaseAuthRequests(BaseTest):
                            ("😁", "🔑", False), ("😀", "", False),
                            ("", "🔑", False), ("", "", False))
         for user, password, valid in test_matrix:
-            status, _ = self.propfind(
-                "/", check=207 if valid else 401, HTTP_AUTHORIZATION=(
-                    "Basic %s" % base64.b64encode(
-                        ("%s:%s" % (user, password)).encode()).decode()))
+            self.propfind("/", check=207 if valid else 401,
+                          HTTP_AUTHORIZATION=("Basic %s" % base64.b64encode(
+                              ("%s:%s" % (user, password)).encode()).decode()))
 
     def test_htpasswd_plain(self):
         self._test_htpasswd("plain", "tmp:bepo")
diff --git a/radicale/xmlutils.py b/radicale/xmlutils.py
index 76961f2..a76f803 100644
--- a/radicale/xmlutils.py
+++ b/radicale/xmlutils.py
@@ -54,25 +54,24 @@ for short, url in NAMESPACES.items():
     ET.register_namespace("" if short == "D" else short, url)
 
 
-def pretty_xml(element, level=0):
+def pretty_xml(element):
     """Indent an ElementTree ``element`` and its children."""
-    if not level:
-        element = copy.deepcopy(element)
-    i = "\n" + level * "  "
-    if len(element) > 0:
-        if not element.text or not element.text.strip():
-            element.text = i + "  "
-        if not element.tail or not element.tail.strip():
-            element.tail = i
-        for sub_element in element:
-            pretty_xml(sub_element, level + 1)
-        if not sub_element.tail or not sub_element.tail.strip():
-            sub_element.tail = i
-    else:
-        if level and (not element.tail or not element.tail.strip()):
-            element.tail = i
-    if not level:
-        return '<?xml version="1.0"?>\n%s' % ET.tostring(element, "unicode")
+    def pretty_xml_recursive(element, level):
+        indent = "\n" + level * "  "
+        if len(element) > 0:
+            if not (element.text or "").strip():
+                element.text = indent + "  "
+            if not (element.tail or "").strip():
+                element.tail = indent
+            for sub_element in element:
+                pretty_xml_recursive(sub_element, level + 1)
+            if not (sub_element.tail or "").strip():
+                sub_element.tail = indent
+        elif level > 0 and not (element.tail or "").strip():
+            element.tail = indent
+    element = copy.deepcopy(element)
+    pretty_xml_recursive(element, 0)
+    return '<?xml version="1.0"?>\n%s' % ET.tostring(element, "unicode")
 
 
 def make_clark(human_tag):
@@ -168,7 +167,7 @@ def props_from_request(xml_request, actions=("set", "remove")):
                     if resource_type.tag == make_clark("C:calendar"):
                         result["tag"] = "VCALENDAR"
                         break
-                    elif resource_type.tag == make_clark("CR:addressbook"):
+                    if resource_type.tag == make_clark("CR:addressbook"):
                         result["tag"] = "VADDRESSBOOK"
                         break
             elif prop.tag == make_clark("C:supported-calendar-component-set"):