Update src/viur/core/bones/string.py

Co-authored-by: Sven Eberth <[email protected]>

src/viur/core/bones/string.py

@@ -128,7 +128,7 @@ def isInvalid(self, value):
             return "Minimum length not reached"
 
         if self.charset:
-            if not all([char in self.charset for char in value]):
+            if any(char not in self.charset for char in value):
                 return "Not all letters are available in the charset"
         return None