Use regexp to check install command output

tests/Composer/Test/Command/InstallCommandTest.php

@@ -155,9 +155,9 @@ class InstallCommandTest extends TestCase
         // Confirm that dependency installation failed and system communicated
         // this with its exit code and text output.
         $this->assertNotEquals(0, $tester->getStatusCode());
-        $this->assertStringContainsString(
+        $this->assertMatchesRegularExpression(
-            'is not found for package test/two',
+            '/is[[:blank:]]+not[[:blank:]]+found[[:blank:]]+for[[:blank:]]+package[[:blank:]]+test\\/two/',
-            \str_replace(PHP_EOL, '', $tester->getDisplay())
+            $tester->getDisplay()
         );
     }