auth: let login helper function return exception to raise instead of raising it self

Make the execution flow more obvious by raising the exception where it matters.

Avoid redundant and potentially misleading return statement that tried to make
it clear that execution wouldn't continue after the function call.

kallithea/lib/auth.py

@@ -700,13 +700,16 b' def set_available_permissions(config):'
 # CHECK DECORATORS
 #==============================================================================
 
-def redirect_to_login(message=None):
+def _redirect_to_login(message=None):
+    """Return an exception that must be raised. It will redirect to the login
+    page which will redirect back to the current URL after authentication.
+    The optional message will be shown in a flash message."""
     from kallithea.lib import helpers as h
-    p = request.path_qs
     if message:
         h.flash(h.literal(message), category='warning')
+    p = request.path_qs
     log.debug('Redirecting to login page, origin: %s', p)
-    raise HTTPFound(location=url('login_home', came_from=p))
+    return HTTPFound(location=url('login_home', came_from=p))
 
 
 class LoginRequired(object):
@@ -731,7 +734,7 b' class LoginRequired(object):'
         log.debug('Checking access for user %s @ %s', user, loc)
 
         if not AuthUser.check_ip_allowed(user, controller.ip_addr):
-            return redirect_to_login(_('IP %s not allowed') % controller.ip_addr)
+            raise _redirect_to_login(_('IP %s not allowed') % controller.ip_addr)
 
         # check if we used an API key and it's a valid one
         api_key = request.GET.get('api_key')
@@ -744,7 +747,7 b' class LoginRequired(object):'
                     return func(*fargs, **fkwargs)
                 else:
                     log.warning('API key ****%s is NOT valid', api_key[-4:])
-                    return redirect_to_login(_('Invalid API key'))
+                    raise _redirect_to_login(_('Invalid API key'))
             else:
                 # controller does not allow API access
                 log.warning('API access to %s is not allowed', loc)
@@ -790,7 +793,7 b' class LoginRequired(object):'
             return func(*fargs, **fkwargs)
         else:
             log.warning('user %s NOT authenticated with regular auth @ %s', user, loc)
-            return redirect_to_login()
+            raise _redirect_to_login()
 
 class NotAnonymous(object):
     """
@@ -807,8 +810,8 b' class NotAnonymous(object):'
         log.debug('Checking if user is not anonymous @%s', cls)
 
         if self.user.is_default_user:
-            return redirect_to_login(_('You need to be a registered user to '
-                    'perform this action'))
+            raise _redirect_to_login(_('You need to be a registered user to '
+                                       'perform this action'))
         else:
             return func(*fargs, **fkwargs)
 
@@ -837,7 +840,7 b' class PermsDecorator(object):'
         else:
             log.debug('Permission denied for %s %s', cls, self.user)
             if self.user.is_default_user:
-                return redirect_to_login(_('You need to be signed in to view this page'))
+                raise _redirect_to_login(_('You need to be signed in to view this page'))
             else:
                 raise HTTPForbidden()