Add test for commit message format

Added test that checks if commits follow the 50/72 git
commit rule and if they are signed (git commit -s).
Fixes: #9, #14.

Signed-off-by: Laura Loghin <lauralg@amazon.com>

integration_tests/utils.py

@@ -1,6 +1,8 @@
 # Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 # SPDX-License-Identifier: Apache-2.0
+
 import os
+import subprocess
 
 
 def get_repo_root_path():
@@ -9,3 +11,11 @@ def get_repo_root_path():
     rust_vmm_ci_path = os.path.dirname(integration_tests_path)
 
     return os.path.dirname(rust_vmm_ci_path)
+
+
+def get_cmd_output(cmd):
+    """Returns stdout content of `cmd` command."""
+    cmd_out = subprocess.run(cmd, shell=True, check=True,
+                             stdout=subprocess.PIPE)
+    stdout = cmd_out.stdout.decode('utf-8')
+    return stdout