Fix #17985: Convert migrationNamespaces to array if needed

Co-authored-by: Alexander Makarov <sam@rmcreative.ru>

framework/CHANGELOG.md

@@ -24,6 +24,7 @@ Yii Framework 2 Change Log
 - Enh #18120: Include path to the log file into error message if `FileTarget::export` fails (uaoleg)
 - Enh #15202: Add optional param `--silent-exit-on-exception` in `yii\console\Controller` (egorrishe)
 - Bug #18110: Add quotes to return value of viewName in MSSQL schema. It is `[someView]` now (darkdef)
+- Bug #17985: Convert migrationNamespaces to array if needed (darkdef)
 
 
 2.0.35 May 02, 2020

framework/console/controllers/BaseMigrateController.php

@@ -119,6 +119,8 @@ abstract class BaseMigrateController extends Controller
                 throw new InvalidConfigException('At least one of `migrationPath` or `migrationNamespaces` should be specified.');
             }
 
+            $this->migrationNamespaces = (array) $this->migrationNamespaces;
+
             foreach ($this->migrationNamespaces as $key => $value) {
                 $this->migrationNamespaces[$key] = trim($value, '\\');
             }