Add MD_STD::exec_edit to run edit and pipe STDERR to a php exception

MD_STD.php

@@ -431,6 +431,23 @@ final class MD_STD {
 
     }
 
+    /**
+     * Wrapper around exec, to be used with editing functions.
+     * Pipes STDERR to STDOUT and throws an Exception on any error.
+     *
+     * @param string $cmds Commands to run.
+     *
+     * @return void
+     */
+    public static function exec_edit(string $cmds):void {
+
+        $error = \exec($cmds . ' 2>&1');
+        if (!empty($error)) {
+            throw new \Exception('Shell error: ' . $error);
+        }
+
+    }
+
     /**
      * Wrapper around levenshtein(), that only compares the first 250
      * characters (levenshtein can't handle more than 255).