Fix example with custom ARGUMENT for extra scripting

docs/projectconf.rst

@@ -621,8 +621,9 @@ Example, specify own upload command for :ref:`platform_atmelavr`:
 .. code-block:: python
 
     Import('env')
+    from base64 import b64decode
 
-    env.Replace(UPLOADHEXCMD='"$UPLOADER" ${ARGUMENTS.get("custom_option")} --uploader --flags')
+    env.Replace(UPLOADHEXCMD='"$UPLOADER" ' + b64decode(ARGUMENTS.get("CUSTOM_OPTION")) + ' --uploader --flags')
 
     # uncomment line below to see environment variables
     # print env.Dump()

platformio/commands/run.py

@@ -203,7 +203,7 @@ class EnvironmentProcessor(object):
             # warn about unknown options
             if k not in self.KNOWN_OPTIONS:
                 click.secho(
-                    "Warning! Ignore unknown `%s` option from `[env:]` section"
+                    "Detected non-PlatformIO `%s` option in `[env:]` section"
                     % k,
                     fg="yellow")
             result[k] = v