bug symfony#21200 [Filesystem] Check that directory is writable after created it in dumpFile() (chalasr)

This PR was merged into the 2.7 branch.

Discussion
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[Filesystem] Check that directory is writable after created it in dumpFile()

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#20612 (comment)
| License       | MIT
| Doc PR        | n/a

In case permissions have been changed meanwhile

Commits
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dbc4148 [Filesystem] Check that the directory is writable after created it in dumpFile()

Author: fabpot

src/Symfony/Component/Filesystem/Filesystem.php

@@ -498,7 +498,9 @@ public function dumpFile($filename, $content, $mode = 0666)
 
         if (!is_dir($dir)) {
             $this->mkdir($dir);
-        } elseif (!is_writable($dir)) {
+        }
+
+        if (!is_writable($dir)) {
             throw new IOException(sprintf('Unable to write to the "%s" directory.', $dir), 0, null, $dir);
         }