Fix deprecated decorator function that didn't work in Python 3

Author: ilanbiala

twilio/jwt/access_token/grants.py

@@ -10,13 +10,11 @@ def deprecated(func):
 
     @functools.wraps(func)
     def new_func(*args, **kwargs):
-        warnings.warn_explicit(
-            "Call to deprecated function {}.".format(func.__name__),
-            category=DeprecationWarning,
-            filename=func.func_code.co_filename,
-            lineno=func.func_code.co_firstlineno + 1
-        )
+        warnings.simplefilter('always', DeprecationWarning)
+        warnings.warn("Call to deprecated function {}.".format(func.__name__), category=DeprecationWarning, stacklevel=2)
+        warnings.simplefilter('default', DeprecationWarning)
         return func(*args, **kwargs)
+
     return new_func