systemd.bbclass: Use bb.fatal() instead of raising FuncFailed

This sets a good example and avoids unnecessarily contributing to
perceived complexity and cargo culting.

Motivating quote below:

< kergoth> the *original* intent was for the function/task to error via
           whatever appropriate means, bb.fatal, whatever, and
           funcfailed was what you'd catch if you were calling
           exec_func/exec_task. that is, it's what those functions
           raise, not what metadata functions should be raising
< kergoth> it didn't end up being used that way
< kergoth> but there's really never a reason to raise it yourself

FuncFailed.__init__ takes a 'name' argument rather than a 'msg'
argument, which also shows that the original purpose got lost.

(From OE-Core rev: 8e956d66087b9c41591b8e4e817ed6c9e42f5981)

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/systemd.bbclass

@@ -165,8 +165,7 @@ python systemd_populate_packages() {
                 if path_found != '':
                     systemd_add_files_and_parse(pkg_systemd, path_found, service, keys)
                 else:
-                    raise bb.build.FuncFailed("SYSTEMD_SERVICE_%s value %s does not exist" % \
-                        (pkg_systemd, service))
+                    bb.fatal("SYSTEMD_SERVICE_%s value %s does not exist" % (pkg_systemd, service))
 
     # Run all modifications once when creating package
     if os.path.exists(d.getVar("D", True)):