Do not allow passwords to be expired for non-local users

lib/Command/ExpirePassword.php

@@ -78,8 +78,10 @@ protected function configure() {
 	protected function execute(InputInterface $input, OutputInterface $output) {
 		$uid = $input->getArgument('uid');
 
-		$exists = $this->userManager->userExists($uid);
-		if($exists === false) {
+		/** @var $user \OCP\IUser */
+		$user = $this->userManager->get($uid);
+
+		if ($user === null) {
 			$output->writeln("<error>Unknown user: $uid</error>");
 			/**
 			 * return EX_NOUSER from /usr/include/sysexits.h
@@ -88,6 +90,11 @@ protected function execute(InputInterface $input, OutputInterface $output) {
 			return 67;
 		}
 
+		if (!$user->canChangePassword()) {
+			$output->writeln("<error>Passwords cannot be expired for user: $uid</error>");
+			return 1;
+		}
+
 		$date = new \DateTime($input->getArgument('expiredate'));
 		$date->setTimezone(new \DateTimeZone('UTC'));
 		$value = $date->format('Y-m-d\TH:i:s\Z'); // ISO8601 with Zulu = UTC