Adjust exception message

src/Composer/Repository/ComposerRepository.php

@@ -468,8 +468,8 @@ class ComposerRepository extends ArrayRepository implements StreamableRepository
                         continue;
                     }
 
-                    $this->io->write('<warning>The contents of '.$filename.' do not match its signature, this is most likely due to a temporary glitch but could indicate a man-in-the-middle attack. Try running composer again and please report it if it still persists.</warning>');
-                    throw new RepositorySecurityException('The contents of '.$filename.' do not match its signature');
+                    // TODO use scarier wording once we know for sure it doesn't do false positives anymore
+                    throw new RepositorySecurityException('The contents of '.$filename.' do not match its signature. This should indicate a man-in-the-middle attack. Try running composer again and report this if you think it is a mistake.');
                 }
                 $data = JsonFile::parseJson($json, $filename);
                 $this->cache->write($cacheKey, $json);

src/Composer/Repository/RepositorySecurityException.php

@@ -3,7 +3,8 @@
 /*
  * This file is part of Composer.
  *
- * (c) 
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
  *
  * For the full copyright and license information, please view the LICENSE
  * file that was distributed with this source code.
@@ -18,5 +19,4 @@ namespace Composer\Repository;
  */
 class RepositorySecurityException extends \Exception
 {
-	// nothing more, standard Exception
 }