diff -u b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
--- b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
@@ -189,8 +189,7 @@
   protected function performUpgrade($register_errors = TRUE) {
 
     // Load the first update screen.
-    $update_url = $GLOBALS['base_url'] . '/core/update.php';
-    $this->upgradeGet($update_url);
+    $this->getUpdatePhp();
     if (!$this->assertResponse(200)) {
       throw new Exception('Initial GET to update.php did not return HTTP 200 status.');
     }
@@ -230,7 +229,7 @@
     }
 
     // Check if there still are pending updates.
-    $this->drupalGet($update_url);
+    $this->getUpdatePhp();
     $this->drupalPost(NULL, array(), t('Continue'));
     if (!$this->assertText(t('No pending updates.'), t('No pending updates at the end of the update process.'))) {
       throw new Exception('update.php still shows pending updates after execution.');
@@ -263,21 +262,16 @@
   }
 
   /**
-   * Retrieves a Drupal 7 absolute path for upgrade.
+   * Gets update.php without calling url().
    *
-   * This function does not call url() to prevent system_list() invocation
-   * before key_value table exists.
-   *
-   * @param $path
-   *   Drupal path or URL to load into internal browser
-   *
-   * @return
-   *   The retrieved HTML string, also available as $this->drupalGetContent()
+   * This function is necessary because drupalGet calls t() before the
+   * database is ready for that.
    */
   protected function upgradeGet($path) {
     // We re-using a CURL connection here. If that connection still has certain
     // options set, it might change the GET into a POST. Make sure we clear out
     // previous options.
+    $path = $GLOBALS['base_url'] . '/core/update.php';
     $out = $this->curlExec(array(CURLOPT_HTTPGET => TRUE, CURLOPT_URL => $path, CURLOPT_NOBODY => FALSE));
     // Ensure that any changes to variables in the other thread are picked up.
     $this->refreshVariables();
@@ -286,7 +280,7 @@
     if ($new = $this->checkForMetaRefresh()) {
       $out = $new;
     }
-    $this->verbose('GET request to: ' . $path .
+    $this->verbose('GET request to: update.php' .
       '<hr />Ending URL: ' . $this->getUrl() .
       '<hr />' . $out);
     return $out;