Add `execute` function (gd_diff.py).

* gd_diff.py (execute): New function.
* tests/test_gd_diff.py (test_execute_success, test_execute_cmderror)
  (test_execute_raise_exception): Tests for `execute` function.

1 files changed, 21 insertions, 0 deletions

diff --git a/gd_diff.py b/gd_diff.py
index 97cf175..3c704e9 100644
--- a/gd_diff.py
+++ b/gd_diff.py
@@ -6,8 +6,12 @@
 #  gns-deb-diff is under the Public Domain. See
 #  <https://creativecommons.org/publicdomain/zero/1.0>
 
+import shlex
 import sys
 
+from subprocess import run, PIPE
+
+
 # list of recognized fields.
 field_list = [
     "Change-Type",
@@ -28,6 +32,23 @@ def read_file(fpath):
     return f.read()
 
 
+def execute(cmd, out=None, err=None):
+    """Run `cmd`. Returns an instance of `subprocess.CompletedProcess`
+
+    `cmd` must be a string containing the command to run.
+    """
+    cmd = shlex.split(cmd)
+
+    try:
+        completed_process = run(cmd, stdout=out, stderr=err)
+    except (FileNotFoundError, OSError, ValueError) as e:
+        print("Error running '%s'\n Error Info:\n %r" % (cmd[0], e),
+              file=sys.stderr)
+        sys.exit(1)
+
+    return completed_process
+
+
 def get_packages(pkgs_file):
     """Return an iterator contaning of package names from `pkgs_file`.