Add common code for fileutils.

This code is present in nova, cinder and also needed by ironic package.
* delete_if_exists
* remove_path_on_error

Also added some tests.

openstack/common/fileutils.py => nova.common.utils <=> cinder.common.utils

Change-Id: Id5001db161bb8e7dfb20d1b2cc2033e886cda32f
Implements: blueprint image-tools

1 files changed, 31 insertions, 0 deletions

diff --git a/openstack/common/fileutils.py b/openstack/common/fileutils.py
index bb2ef61..0c967da 100644
--- a/openstack/common/fileutils.py
+++ b/openstack/common/fileutils.py
@@ -16,9 +16,11 @@
 #    under the License.
 
 
+import contextlib
 import errno
 import os
 
+from openstack.common import excutils
 from openstack.common.gettextutils import _
 from openstack.common import log as logging
 
@@ -65,3 +67,32 @@ def read_cached_file(filename, force_reload=False):
         cache_info['mtime'] = mtime
         reloaded = True
     return (reloaded, cache_info['data'])
+
+
+def delete_if_exists(path):
+    """Delete a file, but ignore file not found error.
+
+    :param path: File to delete
+    """
+
+    try:
+        os.unlink(path)
+    except OSError as e:
+        if e.errno == errno.ENOENT:
+            return
+        else:
+            raise
+
+
+@contextlib.contextmanager
+def remove_path_on_error(path):
+    """Protect code that wants to operate on PATH atomically.
+    Any exception will cause PATH to be removed.
+
+    :param path: File to work with
+    """
+    try:
+        yield
+    except Exception:
+        with excutils.save_and_reraise_exception():
+            delete_if_exists(path)