--- a/libervia/backend/plugins/plugin_xep_0420.py	Tue Jun 18 12:06:45 2024 +0200
+++ b/libervia/backend/plugins/plugin_xep_0420.py	Wed Jun 19 18:44:57 2024 +0200
@@ -50,7 +50,7 @@
     "SCECustomAffix",
     "SCEAffixPolicy",
     "SCEProfile",
-    "SCEAffixValues"
+    "SCEAffixValues",
 ]
 
 
@@ -61,9 +61,9 @@
     C.PI_NAME: "SCE",
     C.PI_IMPORT_NAME: "XEP-0420",
     C.PI_TYPE: "SEC",
-    C.PI_PROTOCOLS: [ "XEP-0420" ],
-    C.PI_DEPENDENCIES: [ "XEP-0334", "XEP-0082" ],
-    C.PI_RECOMMENDATIONS: [ "XEP-0045", "XEP-0033", "XEP-0359" ],
+    C.PI_PROTOCOLS: ["XEP-0420"],
+    C.PI_DEPENDENCIES: ["XEP-0334", "XEP-0082"],
+    C.PI_RECOMMENDATIONS: ["XEP-0045", "XEP-0033", "XEP-0359"],
     C.PI_MAIN: "XEP_0420",
     C.PI_HANDLER: "no",
     C.PI_DESCRIPTION: D_("Implementation of Stanza Content Encryption"),
@@ -240,7 +240,7 @@
         NS_ADDRESS,
         # Not part of the specification (yet), but just doesn't make sense in an encrypted
         # envelope:
-        NS_EME
+        NS_EME,
     }
 
     # Set of (namespace, element name) tuples that define elements which are never allowed
@@ -331,8 +331,7 @@
             rpad_length = max(0, 53 - content_byte_size_diff) + secrets.randbelow(201)
             rpad_content = "".join(
                 secrets.choice(string.digits + string.ascii_letters + string.punctuation)
-                for __
-                in range(rpad_length)
+                for __ in range(rpad_length)
             )
             envelope.addElement((NS_SCE, "rpad"), content=rpad_content)
 
@@ -370,9 +369,7 @@
 
     @staticmethod
     def unpack_stanza(
-        profile: SCEProfile,
-        stanza: domish.Element,
-        envelope_serialized: bytes
+        profile: SCEProfile, stanza: domish.Element, envelope_serialized: bytes
     ) -> SCEAffixValues:
         """Unpack a stanza packed according to Stanza Content Encryption.
 
@@ -409,18 +406,21 @@
         custom_affixes = set(profile.custom_policies.keys())
 
         # Make sure the envelope adheres to the schema
-        parser = etree.XMLParser(schema=etree.XMLSchema(etree.XML(ENVELOPE_SCHEMA.format(
-            custom_affix_references="".join(
-                f'<xs:element ref="{custom_affix.element_name}" minOccurs="0"/>'
-                for custom_affix
-                in custom_affixes
-            ),
-            custom_affix_definitions="".join(
-                custom_affix.element_schema
-                for custom_affix
-                in custom_affixes
+        parser = etree.XMLParser(
+            schema=etree.XMLSchema(
+                etree.XML(
+                    ENVELOPE_SCHEMA.format(
+                        custom_affix_references="".join(
+                            f'<xs:element ref="{custom_affix.element_name}" minOccurs="0"/>'
+                            for custom_affix in custom_affixes
+                        ),
+                        custom_affix_definitions="".join(
+                            custom_affix.element_schema for custom_affix in custom_affixes
+                        ),
+                    ).encode("utf-8")
+                )
             )
-        ).encode("utf-8"))))
+        )
 
         try:
             etree.fromstring(envelope_serialized_string, parser)
@@ -435,20 +435,16 @@
 
         # Verify the affixes
         rpad_element = cast(
-            Optional[domish.Element],
-            next(envelope.elements(NS_SCE, "rpad"), None)
+            Optional[domish.Element], next(envelope.elements(NS_SCE, "rpad"), None)
         )
         time_element = cast(
-            Optional[domish.Element],
-            next(envelope.elements(NS_SCE, "time"), None)
+            Optional[domish.Element], next(envelope.elements(NS_SCE, "time"), None)
         )
         to_element = cast(
-            Optional[domish.Element],
-            next(envelope.elements(NS_SCE, "to"), None)
+            Optional[domish.Element], next(envelope.elements(NS_SCE, "to"), None)
         )
         from_element = cast(
-            Optional[domish.Element],
-            next(envelope.elements(NS_SCE, "from"), None)
+            Optional[domish.Element], next(envelope.elements(NS_SCE, "from"), None)
         )
 
         # The rpad doesn't need verification.
@@ -456,8 +452,11 @@
 
         # The time affix isn't verified other than that the timestamp is parseable.
         try:
-            timestamp_value = None if time_element is None else \
-                XEP_0082.parse_datetime(time_element["stamp"])
+            timestamp_value = (
+                None
+                if time_element is None
+                else XEP_0082.parse_datetime(time_element["stamp"])
+            )
         except ValueError as e:
             raise AffixVerificationFailed("Malformed time affix.") from e
 
@@ -513,25 +512,26 @@
             element_name = affix.element_name
             element = cast(
                 Optional[domish.Element],
-                next(envelope.elements(NS_SCE, element_name), None)
+                next(envelope.elements(NS_SCE, element_name), None),
             )
             if element is not None:
                 affix.verify(stanza, element)
                 custom_values[affix] = element
 
         # Check whether all affixes required by the profile are present
-        rpad_missing = \
+        rpad_missing = (
             profile.rpad_policy is SCEAffixPolicy.REQUIRED and rpad_element is None
-        time_missing = \
+        )
+        time_missing = (
             profile.time_policy is SCEAffixPolicy.REQUIRED and time_element is None
-        to_missing = \
-            profile.to_policy is SCEAffixPolicy.REQUIRED and to_element is None
-        from_missing = \
+        )
+        to_missing = profile.to_policy is SCEAffixPolicy.REQUIRED and to_element is None
+        from_missing = (
             profile.from_policy is SCEAffixPolicy.REQUIRED and from_element is None
+        )
         custom_missing = any(
             affix not in custom_values
-            for affix, policy
-            in profile.custom_policies.items()
+            for affix, policy in profile.custom_policies.items()
             if policy is SCEAffixPolicy.REQUIRED
         )
 
@@ -570,9 +570,5 @@
                 stanza.addChild(child)
 
         return SCEAffixValues(
-            rpad_value,
-            timestamp_value,
-            recipient_value,
-            sender_value,
-            custom_values
+            rpad_value, timestamp_value, recipient_value, sender_value, custom_values
         )