skip tests with extra requirements

tests/colocated_python_test.py

@@ -15,6 +15,7 @@
 import threading
 import time
 from typing import Sequence
+import unittest
 
 from absl.testing import absltest
 from absl.testing import parameterized
@@ -30,6 +31,10 @@
 config.parse_flags_with_absl()
 jtu.request_cpu_devices(8)
 
+try:
+  import cloudpickle  # noqa
+except (ModuleNotFoundError, ImportError):
+  raise unittest.SkipTest("tests depend on cloudpickle library")
 
 def _colocated_cpu_devices(
     devices: Sequence[jax.Device],

tests/export_test.py

@@ -292,6 +292,7 @@ def f(a_b_pair, a, b):
                         exp_f.call((a, b), a=a, b=b))
 
   def test_pytree_namedtuple(self):
+    if not CAN_SERIALIZE: raise unittest.SkipTest("test requires flatbuffers")
     T = collections.namedtuple("SomeType", ("a", "b", "c"))
     export.register_namedtuple_serialization(
         T,
@@ -317,6 +318,7 @@ def f(x):
                      tree_util.tree_structure(res))
 
   def test_pytree_namedtuple_error(self):
+    if not CAN_SERIALIZE: raise unittest.SkipTest("test requires flatbuffers")
     T = collections.namedtuple("SomeType", ("a", "b"))
     x = T(a=1, b=2)
     with self.assertRaisesRegex(
@@ -363,6 +365,7 @@ def test_pytree_namedtuple_error(self):
       )
 
   def test_pytree_custom_types(self):
+    if not CAN_SERIALIZE: raise unittest.SkipTest("test requires flatbuffers")
     x1 = collections.OrderedDict([("foo", 34), ("baz", 101), ("something", -42)])
 
     @tree_util.register_pytree_node_class