Set selected library to default before checks (apache#36156)

Author: claudevdm

sdks/python/apache_beam/internal/pickler.py

@@ -80,6 +80,9 @@ def set_library(selected_library=DEFAULT_PICKLE_LIB):
   """ Sets pickle library that will be used. """
   global desired_pickle_lib
 
+  if selected_library == 'default':
+    selected_library = DEFAULT_PICKLE_LIB
+
   if selected_library == USE_DILL and not dill_pickler:
     raise ImportError(
         "Pipeline option pickle_library=dill is set, but dill is not "
@@ -98,9 +101,6 @@ def set_library(selected_library=DEFAULT_PICKLE_LIB):
   if is_currently_dill != dill_is_requested:
     dill_pickler.override_pickler_hooks(selected_library == USE_DILL)
 
-  if selected_library == 'default':
-    selected_library = DEFAULT_PICKLE_LIB
-
   if dill_is_requested:
     desired_pickle_lib = dill_pickler
   elif selected_library == USE_CLOUDPICKLE: