avoid race condition in append test

Author: alimanfoo

zarr/core.py

@@ -986,6 +986,8 @@ def _append_nosync(self, data, axis=0):
         )
         self[append_selection] = data
 
+        return new_shape
+
     def view(self, shape=None, chunks=None, dtype=None,
              fill_value=None, filters=None, read_only=None,
              synchronizer=None):

zarr/tests/test_sync.py

@@ -54,8 +54,8 @@ def _append(arg):
     import numpy as np
     x = np.empty(1000, dtype='i4')
     x[:] = i
-    z.append(x)
-    return z.shape
+    shape = z.append(x)
+    return shape
 
 
 def _set_arange(arg):