lib/oe/package_manager.py: check that package list is not empty

If we're just attempting to install packages and the package list is
empty, just return.

(From OE-Core rev: 8bf5d80e3502a71fdda688aace0799b47ae19b3b)

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oe/package_manager.py

@@ -496,7 +496,7 @@ class RpmPM(PackageManager):
     def install(self, pkgs, attempt_only=False):
 
         bb.note("Installing the following packages: %s" % ' '.join(pkgs))
-        if len(pkgs) == 0:
+        if attempt_only and len(pkgs) == 0:
             return
         pkgs = self._pkg_translate_oe_to_smart(pkgs, attempt_only)
 
@@ -907,6 +907,9 @@ class OpkgPM(PackageManager):
         self.deploy_dir_unlock()
 
     def install(self, pkgs, attempt_only=False):
+        if attempt_only and len(pkgs) == 0:
+            return
+
         cmd = "%s %s install %s" % (self.opkg_cmd, self.opkg_args, ' '.join(pkgs))
 
         os.environ['D'] = self.target_rootfs
@@ -1164,6 +1167,9 @@ class DpkgPM(PackageManager):
         self.deploy_dir_unlock()
 
     def install(self, pkgs, attempt_only=False):
+        if attempt_only and len(pkgs) == 0:
+            return
+
         os.environ['APT_CONFIG'] = self.apt_conf_file
 
         cmd = "%s %s install --force-yes --allow-unauthenticated %s" % \