imagefeatures: New test case, test_empty_image, added

An empty image build file exists under the meta-selftest folder, test-empty-image.bb,
which builds an image with no additional packages. However, there were no further
selftest created to verify its emptiness

This change consists of the selftest related to the said image to verify its
emptiness and the 'import glob' moved as global import instead of local import.

The expected outcome of the test should be TRUE or 1 if the .manifest file content
is empty.

[YOCTO #8455]

(From OE-Core rev: 1f8bdaa746c6e7efc07789256d5c050780c81f4c)

Signed-off-by: Khairul Rohaizzat Jamaluddin <khairul.rohaizzat.jamaluddin@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/selftest/cases/imagefeatures.py

@@ -5,6 +5,7 @@
 from oeqa.selftest.case import OESelftestTestCase
 from oeqa.utils.commands import runCmd, bitbake, get_bb_var, runqemu
 from oeqa.utils.sshcontrol import SSHControl
+import glob
 import os
 import json
 
@@ -347,7 +348,7 @@ UBOOT_ENTRYPOINT = "0x80080000"
         Author:      Humberto Ibarra <humberto.ibarra.lopez@intel.com>
                      Yeoh Ee Peng <ee.peng.yeoh@intel.com>
         """
-        import glob
+      
         image_name = 'core-image-minimal'
         features = 'IMAGE_GEN_DEBUGFS = "1"\n'
         features += 'IMAGE_FSTYPES_DEBUGFS = "tar.bz2"\n'
@@ -368,3 +369,12 @@ UBOOT_ENTRYPOINT = "0x80080000"
         for t in dbg_symbols_targets:
             result = runCmd('objdump --syms %s | grep debug' % t)
             self.assertTrue("debug" in result.output, msg='Failed to find debug symbol: %s' % result.output)
+
+    def test_empty_image(self):
+        """Test creation of image with no packages"""
+        bitbake('test-empty-image')
+        res_dir = get_bb_var('DEPLOY_DIR_IMAGE')
+        images = os.path.join(res_dir, "test-empty-image-*.manifest")
+        result = glob.glob(images)
+        with open(result[1],"r") as f:
+                self.assertEqual(len(f.read().strip()),0)