Merge #2056

2056: Passlib r=mergify[bot] a=ghostwheel42

## What type of PR?

minor bug-fix

## What does this PR do?

compiles list of schemes using an iterator. will not fail when `scrypt` is not present in registry.

### Related issue(s)

updates #1753

## Prerequisites
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ ] In case of feature or enhancement: documentation updated accordingly
- [ ] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Alexander Graf <ghostwheel42@users.noreply.github.com>

core/admin/mailu/models.py

@@ -551,13 +551,13 @@ class User(Base, Email):
         if cls._ctx:
             return cls._ctx
 
-        schemes = passlib.registry.list_crypt_handlers()
-        # scrypt throws a warning if the native wheels aren't found
-        schemes.remove('scrypt')
-        # we can't leave plaintext schemes as they will be misidentified
-        for scheme in schemes:
-            if scheme.endswith('plaintext'):
-                schemes.remove(scheme)
+        # compile schemes
+        # - skip scrypt (throws a warning if the native wheels aren't found)
+        # - skip plaintext schemes (will be misidentified)
+        schemes = [
+            scheme for scheme in passlib.registry.list_crypt_handlers()
+            if not (scheme == 'scrypt' or scheme.endswith('plaintext'))
+        ]
         cls._ctx = passlib.context.CryptContext(
             schemes=schemes,
             default='bcrypt_sha256',