Add support for NO_COLOR environment variable.

Based on the recommendations on https://no-color.org/

Refs #14147

src/Console/ConsoleOutput.php

@@ -175,6 +175,9 @@ class ConsoleOutput
             (
                 function_exists('posix_isatty') &&
                 !posix_isatty($this->_output)
+            ) ||
+            (
+                env('NO_COLOR') !== null
             )
         ) {
             $this->_outputAs = self::PLAIN;

tests/TestCase/Console/ConsoleOutputTest.php

@@ -56,6 +56,15 @@ class ConsoleOutputTest extends TestCase
         unset($this->output);
     }
 
+    public function testNoColorEnvironmentVariable()
+    {
+        $_SERVER['NO_COLOR'] = '1';
+        $output = new ConsoleOutput();
+        $this->assertSame(ConsoleOutput::PLAIN, $output->getOutputAs());
+
+        unset($_SERVER['NO_COLOR']);
+    }
+
     /**
      * test writing with no new line
      *