bug #25816 Problem in phar see mergerequest #25579 (betzholz)

This PR was squashed before being merged into the 2.7 branch (closes #25816).

Discussion
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Problem in phar see mergerequest #25579

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #... <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | symfony/symfony-docs#... <!--highly recommended for new features-->

If packed into phar the old version creates path like 'file:///phar%3A/'. see symfony/symfony#25579

Commits
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3e0c8ffb43 Problem in phar see mergerequest #25579

Author: fabpot

Loader/XmlFileLoader.php

@@ -458,16 +458,20 @@ public function validateSchema(\DOMDocument $dom)
         $imports = '';
         foreach ($schemaLocations as $namespace => $location) {
             $parts = explode('/', $location);
+            $locationstart = 'file:///';
             if (0 === stripos($location, 'phar://')) {
                 $tmpfile = tempnam(sys_get_temp_dir(), 'sf2');
                 if ($tmpfile) {
                     copy($location, $tmpfile);
                     $tmpfiles[] = $tmpfile;
                     $parts = explode('/', str_replace('\\', '/', $tmpfile));
+                } else {
+                    array_shift($parts);
+                    $locationstart = 'phar:///';
                 }
             }
             $drive = '\\' === DIRECTORY_SEPARATOR ? array_shift($parts).'/' : '';
-            $location = 'file:///'.$drive.implode('/', array_map('rawurlencode', $parts));
+            $location = $locationstart.$drive.implode('/', array_map('rawurlencode', $parts));
 
             $imports .= sprintf('  <xsd:import namespace="%s" schemaLocation="%s" />'."\n", $namespace, $location);
         }