tests: add docstrings & print_function (for Python 3)

Bug: https://crbug.com/gerrit/10418
Change-Id: Id98183597a9b0201ca98ec0bf5033a5f5ac6bda2
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/232892
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: David Pursehouse <dpursehouse@collab.net>

tests/test_git_command.py

@@ -14,6 +14,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""Unittests for the git_command.py module."""
+
+from __future__ import print_function
+
 import unittest
 
 import git_command

tests/test_git_config.py

@@ -14,6 +14,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""Unittests for the git_config.py module."""
+
+from __future__ import print_function
+
 import os
 import unittest
 

tests/test_project.py

@@ -14,6 +14,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""Unittests for the project.py module."""
+
+from __future__ import print_function
+
 import unittest
 
 import project

tests/test_wrapper.py

@@ -14,6 +14,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""Unittests for the wrapper.py module."""
+
+from __future__ import print_function
+
 import os
 import unittest