fix test and coverage failures

Author: alimanfoo

requirements_dev.txt

@@ -15,6 +15,7 @@ idna==2.6
 mccabe==0.6.1
 monotonic==1.3
 msgpack-python==0.4.8
+nose==1.3.7
 numcodecs==0.5.2
 numpy==1.13.3
 packaging==16.8

zarr/tests/test_core.py

@@ -1272,7 +1272,7 @@ def test_nbytes_stored(self):
 
 try:
     import lmdb
-except ImportError:
+except ImportError:  # pragma: no cover
     lmdb = None
 
 

zarr/tests/test_hierarchy.py

@@ -905,7 +905,7 @@ def create_store():
 
 try:
     import lmdb
-except ImportError:
+except ImportError:  # pragma: no cover
     lmdb = None
 
 

zarr/tests/test_storage.py

@@ -793,7 +793,6 @@ def create_store(self):
     except ImportError:  # pragma: no cover
         ndbm = None
 
-
     @pytest.mark.skipif(ndbm is None, reason='ndbm is not installed')
     class TestDBMStoreNDBM(TestDBMStore):
 
@@ -822,7 +821,7 @@ def create_store(self):
 
 try:
     import lmdb
-except ImportError:
+except ImportError:  # pragma: no cover
     lmdb = None