7 files declare their use of RouteNotFoundException

ChainMatcher.php in drupal/core/lib/Drupal/Core/Routing/ChainMatcher.php
Definition of Drupal\Core\Routing\ChainMatcher.
ChainMatcherTest.php in drupal/core/modules/system/lib/Drupal/system/Tests/Routing/ChainMatcherTest.php
Definition of Drupal\system\Tests\Routing\ChainMatcherTest.
MimeTypeMatcher.php in drupal/core/lib/Drupal/Core/Routing/MimeTypeMatcher.php
Contains Drupal\Core\Routing\MimeTypeMatcher.
MimeTypeMatcherTest.php in drupal/core/modules/system/lib/Drupal/system/Tests/Routing/MimeTypeMatcherTest.php
Contains Drupal\system\Tests\Routing\MimeTypeMatcherTest.
MockMatcher.php in drupal/core/modules/system/lib/Drupal/system/Tests/Routing/MockMatcher.php
Definition of Drupal\system\Tests\Routing\MockMatcher.
UrlGenerator.php in drupal/core/vendor/symfony/routing/Symfony/Component/Routing/Generator/UrlGenerator.php
UrlGeneratorInterface.php in drupal/core/vendor/symfony/routing/Symfony/Component/Routing/Generator/UrlGeneratorInterface.php