merged branch Seldaek/proctemp (PR #7066)

This PR was merged into the 2.1 branch.

Commits
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5e8d844 [Process] Warn user with a useful message when tmpfile() failed

Discussion
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[Process] Warn user with a useful message when tmpfile() failed

Simple warning so users know what's going on instead of getting a proc_open error, see composer/composer#1581.

Can't get the PR template since ~~symfony.com~~ my dns resolver is dead :)

src/Symfony/Component/Process/Process.php

@@ -213,6 +213,9 @@ class Process
             $this->fileHandles = array(
                 self::STDOUT => tmpfile(),
             );
+            if (false === $this->fileHandles[self::STDOUT]) {
+                throw new RuntimeException('A temporary file could not be opened to write the process output to, verify that your TEMP environment variable is writable');
+            }
             $this->readBytes = array(
                 self::STDOUT => 0,
             );