misc: use force_str in lazy variables (#36515)

wcs/variables.py

@@ -16,6 +16,7 @@
 
 import warnings
 
+from django.utils import six
 from django.utils.encoding import force_text
 from django.utils.functional import SimpleLazyObject
 
@@ -23,7 +24,7 @@ from quixote import get_publisher, get_request
 
 from pyproj import Geod
 
-from .qommon import misc
+from .qommon import misc, force_str
 from .qommon.evalutils import make_datetime
 from .qommon.templatetags.qommon import parse_datetime
 from .qommon.storage import (Or, Equal, NotEqual)
@@ -519,9 +520,9 @@ class LazyFieldVar(object):
 
     def __str__(self):
         value = self.get_value()
-        if isinstance(value, unicode):
-            return value.encode(get_publisher().site_charset)
-        return str(value)
+        if not isinstance(value, six.string_types):
+            value = str(value)
+        return force_str(value)
 
     def __nonzero__(self):
         if self._field.key == 'bool':