Merge branch '3.4' into 4.4

* 3.4:
  [PhpUnitBridge] fix bad detection of unsilenced deprecations
  [HttpKernel] Fix error logger when stderr is redirected to /dev/null (FPM)

Author: nicolas-grekas

Log/Logger.php

@@ -37,10 +37,10 @@ class Logger extends AbstractLogger
     private $formatter;
     private $handle;
 
-    public function __construct(string $minLevel = null, $output = 'php://stderr', callable $formatter = null)
+    public function __construct(string $minLevel = null, $output = null, callable $formatter = null)
     {
         if (null === $minLevel) {
-            $minLevel = 'php://stdout' === $output || 'php://stderr' === $output ? LogLevel::CRITICAL : LogLevel::WARNING;
+            $minLevel = null === $output || 'php://stdout' === $output || 'php://stderr' === $output ? LogLevel::ERROR : LogLevel::WARNING;
 
             if (isset($_ENV['SHELL_VERBOSITY']) || isset($_SERVER['SHELL_VERBOSITY'])) {
                 switch ((int) (isset($_ENV['SHELL_VERBOSITY']) ? $_ENV['SHELL_VERBOSITY'] : $_SERVER['SHELL_VERBOSITY'])) {
@@ -58,7 +58,7 @@ public function __construct(string $minLevel = null, $output = 'php://stderr', c
 
         $this->minLevelIndex = self::$levels[$minLevel];
         $this->formatter = $formatter ?: [$this, 'format'];
-        if (false === $this->handle = \is_resource($output) ? $output : @fopen($output, 'a')) {
+        if ($output && false === $this->handle = \is_resource($output) ? $output : @fopen($output, 'a')) {
             throw new InvalidArgumentException(sprintf('Unable to open "%s".', $output));
         }
     }
@@ -79,10 +79,14 @@ public function log($level, $message, array $context = [])
         }
 
         $formatter = $this->formatter;
-        @fwrite($this->handle, $formatter($level, $message, $context));
+        if ($this->handle) {
+            @fwrite($this->handle, $formatter($level, $message, $context));
+        } else {
+            error_log($formatter($level, $message, $context, false));
+        }
     }
 
-    private function format(string $level, string $message, array $context): string
+    private function format(string $level, string $message, array $context, bool $prefixDate = true): string
     {
         if (false !== strpos($message, '{')) {
             $replacements = [];
@@ -101,6 +105,11 @@ private function format(string $level, string $message, array $context): string
             $message = strtr($message, $replacements);
         }
 
-        return sprintf('%s [%s] %s', date(\DateTime::RFC3339), $level, $message).PHP_EOL;
+        $log = sprintf('[%s] %s', $level, $message).PHP_EOL;
+        if ($prefixDate) {
+            $log = date(\DateTime::RFC3339).' '.$log;
+        }
+
+        return $log;
     }
 }