RouteNotFoundException: Route "path_delete" does not exist

While it doesn't seem to hurt anything, every time I run drush si, I get this:

You are about to DROP all tables in your '8x' database. Do you want to continue? (y/n): y
Starting Drupal installation. This takes a few seconds ...           [ok]
WD menu: Symfony\Component\Routing\Exception\RouteNotFoundException: [error]
Route "path_delete" does not exist. in
Drupal\Core\Routing\RouteProvider->getRouteByName() (line 146 of
/Users/webchick/Sites/8.x/core/lib/Drupal/Core/Routing/RouteProvider.php).
WD menu: Symfony\Component\Routing\Exception\RouteNotFoundException: [error]
Route "path_delete" does not exist. in
Drupal\Core\Routing\RouteProvider->getRouteByName() (line 146 of
/Users/webchick/Sites/8.x/core/lib/Drupal/Core/Routing/RouteProvider.php).
WD menu: Symfony\Component\Routing\Exception\RouteNotFoundException: [error]
Route "path_delete" does not exist. in
Drupal\Core\Routing\RouteProvider->getRouteByName() (line 146 of
/Users/webchick/Sites/8.x/core/lib/Drupal/Core/Routing/RouteProvider.php).
Installation complete.  User name: admin  User password: admin       [ok]
All necessary changes to sites/default and sites/default/settings.php[warning]
have been made, so you should remove write permissions to them now in
order to avoid security risks. If you are unsure how to do so,
consult the online handbook.

With --debug on, I notice these errors occur right between:

WD system: tour module installed. [18.18 sec, 88.51 MB]                   [info]
WD system: tour module enabled. [18.18 sec, 88.3 MB]                      [info]

(which seems to be the last module, other than "update," which comes at the end)

...and:

WD system: standard module installed. [22.24 sec, 88.72 MB]               [info]
WD system: standard module enabled. [22.24 sec, 88.43 MB]                 [info]

I hope this is not a duplicate; I searched for both RouteNotFoundException and path_delete and didn't find anything.