Add mandatory headers to files touched by this branch
diff --git a/tests/primitives/test_block.py b/tests/primitives/test_block.py
index 0407b0f..774409c 100644
--- a/tests/primitives/test_block.py
+++ b/tests/primitives/test_block.py
@@ -11,6 +11,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import, division, print_function
+
 import binascii
 
 import pretend