minor #54387 [Filesystem] fix tests on Windows (xabbuh)

This PR was merged into the 7.1 branch.

Discussion
----------

[Filesystem]  fix tests on Windows

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        |
| License       | MIT

Commits
-------

3dc9c4e fix tests on Windows

src/Symfony/Component/Filesystem/Tests/FilesystemTest.php

@@ -1812,15 +1812,15 @@ public function testReadFile()
     public function testReadNonExistentFile()
     {
         $this->expectException(IOException::class);
-        $this->expectExceptionMessageMatches('#^Failed to read file ".+/Tests/invalid"\\: file_get_contents\\(.+/Tests/invalid\\)\\: Failed to open stream\\: No such file or directory$#');
+        $this->expectExceptionMessageMatches(sprintf('#^Failed to read file ".+%1$sTests/invalid"\\: file_get_contents\\(.+%1$sTests/invalid\\)\\: Failed to open stream\\: No such file or directory$#', preg_quote(\DIRECTORY_SEPARATOR)));
 
         $this->filesystem->readFile(__DIR__.'/invalid');
     }
 
     public function testReadDirectory()
     {
         $this->expectException(IOException::class);
-        $this->expectExceptionMessageMatches('#^Failed to read file ".+/Tests"\\: File is a directory\\.$#');
+        $this->expectExceptionMessageMatches(sprintf('#^Failed to read file ".+%sTests"\\: File is a directory\\.$#', preg_quote(\DIRECTORY_SEPARATOR)));
 
         $this->filesystem->readFile(__DIR__);
     }