util: Add a utility for managing temporary files

In multiple situations we need to create temporary files or directories
that should not be preserved after compose is finished. Let's add
context managers that ensure these get cleaned up.

This fixes tests leaving garbage around in /tmp.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/util.py

@@ -25,6 +25,7 @@ import re
 import urlparse
 import contextlib
 import traceback
+import tempfile
 
 from kobo.shortcuts import run, force_list
 from productmd.common import get_major_version
@@ -572,3 +573,22 @@ def levenshtein(a, b):
                             mat[j - 1][i - 1] + cost)
 
     return mat[len(b)][len(a)]
+
+
+@contextlib.contextmanager
+def temp_dir(log=None, *args, **kwargs):
+    """Create a temporary directory and ensure it's deleted."""
+    if kwargs.get('dir'):
+        # If we are supposed to create the temp dir in a particular location,
+        # ensure the location already exists.
+        makedirs(kwargs['dir'])
+    dir = tempfile.mkdtemp(*args, **kwargs)
+    try:
+        yield dir
+    finally:
+        try:
+            shutil.rmtree(dir)
+        except OSError as exc:
+            # Okay, we failed to delete temporary dir.
+            if log:
+                log.warning('Error removing %s: %s', dir, exc.strerror)