Don't check quotes when attributes are built from tokens.

mwparserfromhell/nodes/extras/attribute.py

@@ -37,9 +37,9 @@ class Attribute(StringMixIn):
     """
 
     def __init__(self, name, value=None, quotes='"', pad_first=" ",
-                 pad_before_eq="", pad_after_eq=""):
+                 pad_before_eq="", pad_after_eq="", check_quotes=True):
         super(Attribute, self).__init__()
-        if not quotes and self._value_needs_quotes(value):
+        if check_quotes and not quotes and self._value_needs_quotes(value):
             raise ValueError("given value {0!r} requires quotes".format(value))
         self._name = name
         self._value = value

mwparserfromhell/parser/builder.py

@@ -237,7 +237,8 @@ class Builder(object):
                 else:
                     name, value = self._pop(), None
                 return Attribute(name, value, quotes, start.pad_first,
-                                 start.pad_before_eq, start.pad_after_eq)
+                                 start.pad_before_eq, start.pad_after_eq,
+                                 check_quotes=False)
             else:
                 self._write(self._handle_token(token))
         raise ParserError("_handle_attribute() missed a close token")