sign_rpm_ext.bbclass: clean up

Signed-off-by: Jia Zhang <lans.zhang2008@gmail.com>

meta-integrity/classes/sign_rpm_ext.bbclass

@@ -2,10 +2,6 @@
 # environment. By default, the values for the sample keys are configured
 # in meta-signing-key.
 
-RPM_GPG_BACKEND ?= "local"
-# SHA-256 is used for the file checksum digest.
-RPM_FILE_CHECKSUM_DIGEST ?= "8"
-
 RPM_SIGN_FILES = "${@bb.utils.contains('DISTRO_FEATURES', 'ima', '1', '0', d)}"
 # By default, the values below are applicable for the sample keys provided
 # by meta-signing-key.
@@ -15,17 +11,13 @@ RPM_FSK_PASSWORD ?= "password"
 inherit sign_rpm user-key-store
 
 python () {
-    if d.getVar('RPM_SIGN_FILES', True) != '1':
-        return
-
     gpg_path = d.getVar('GPG_PATH', True)
     if not gpg_path:
         gpg_path = d.getVar('DEPLOY_DIR_IMAGE', True) + '/.gnupg'
         d.setVar('GPG_PATH', gpg_path)
 
     if not os.path.exists(gpg_path):
-        cmd = ' '.join(('mkdir -p', gpg_path))
-        status, output = oe.utils.getstatusoutput(cmd)
+        status, output = oe.utils.getstatusoutput('mkdir -p %s' % gpg_path)
         if status:
             raise bb.build.FuncFailed('Failed to create gpg keying %s: %s' %
                                       (gpg_path, output))