Fix homebrew linked/unlinked output.

library/packaging/homebrew

@@ -626,10 +626,18 @@ class Homebrew(object):
                if opt]
 
         rc, out, err = self.module.run_command(cmd)
+
+        if rc == 0:
             self.changed_count += 1
             self.changed = True
             self.message = 'Package linked: {0}'.format(self.current_package)
 
+            return True
+        else:
+            self.failed = True
+            self.message = 'Package could not be linked: {0}.'.format(self.current_package)
+            raise HomebrewException(self.message)
+
     def _link_packages(self):
         for package in self.packages:
             self.current_package = package
@@ -662,10 +670,18 @@ class Homebrew(object):
                if opt]
 
         rc, out, err = self.module.run_command(cmd)
+
+        if rc == 0:
             self.changed_count += 1
             self.changed = True
             self.message = 'Package unlinked: {0}'.format(self.current_package)
 
+            return True
+        else:
+            self.failed = True
+            self.message = 'Package could not be unlinked: {0}.'.format(self.current_package)
+            raise HomebrewException(self.message)
+
     def _unlink_packages(self):
         for package in self.packages:
             self.current_package = package