Correctly identify Oracle Linux OSes

libguestfs prior to 1.27.9 will identify Oracle Linux as Red Hat
Enterprise Linux. Check for the presence of /etc/oracle-linux to
determine if the OS is Oracle Linux.

image_creator/os_type/rhel.py

+# -*- coding: utf-8 -*-
+#
+# Copyright 2014 GRNET S.A. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or
+# without modification, are permitted provided that the following
+# conditions are met:
+#
+#   1. Redistributions of source code must retain the above
+#      copyright notice, this list of conditions and the following
+#      disclaimer.
+#
+#   2. Redistributions in binary form must reproduce the above
+#      copyright notice, this list of conditions and the following
+#      disclaimer in the documentation and/or other materials
+#      provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
+# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# The views and conclusions contained in the software and
+# documentation are those of the authors and should not be
+# interpreted as representing official policies, either expressed
+# or implied, of GRNET S.A.
+
+"""This module hosts OS-specific code for Red Hat Enterprise Linux"""
+
+from image_creator.os_type.linux import Linux
+
+
+class Rhel(Linux):
+    "OS class for Red Hat Enterprise Linux"""
+
+    def _do_collect_metadata(self):
+        """Collect metadata about the OS"""
+        super(Rhel, self)._do_collect_metadata()
+
+        # Check if the image is Oracle Linux
+        oracle = '/etc/oracle-release'
+        if self.image.g.is_file(oracle):
+            self.meta['OS'] = 'oraclelinux'
+            self.meta['DESCRIPTION'] = self.image.g.head_n(1, oracle)[0]
+
+
+# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :