don't import plasma errors directly into top level pyarrow module

python/pyarrow/__init__.py

@@ -148,11 +148,6 @@ from pyarrow.ipc import (Message, MessageReader,
                          serialize_pandas, deserialize_pandas)
 import pyarrow.ipc as ipc
 
-try:
-    from pyarrow.plasma import PlasmaObjectExists, PlasmaStoreFull
-except:
-    pass
-
 
 def open_stream(source):
     """

python/pyarrow/tests/test_plasma.py

@@ -227,7 +227,7 @@ class TestPlasmaClient(object):
         # Make sure that creating the same object twice raises an exception.
         object_id = random_object_id()
         self.plasma_client.create_and_seal(object_id, b'a', b'b')
-        with pytest.raises(pa.PlasmaObjectExists):
+        with pytest.raises(pa.plasma.PlasmaObjectExists):
             self.plasma_client.create_and_seal(object_id, b'a', b'b')
 
         # Make sure that these objects can be evicted.
@@ -852,7 +852,7 @@ class TestPlasmaClient(object):
         for _ in range(2):
             create_object(self.plasma_client2, DEFAULT_PLASMA_STORE_MEMORY, 0)
         # Verify that an object that is too large does not fit.
-        with pytest.raises(pa.PlasmaStoreFull):
+        with pytest.raises(pa.plasma.PlasmaStoreFull):
             create_object(self.plasma_client2,
                           DEFAULT_PLASMA_STORE_MEMORY + SMALL_OBJECT_SIZE, 0)