config dump --format json provides an invalid JSON format

[kittaakos]

Bug Report

Current behavior

arduino-cli config dump --format json

Provides an invalid JSON format.

proxy_type: auto
sketchbook_path: /Users/akos.kitta/Documents/Arduino
arduino_data: /Users/akos.kitta/Library/Arduino15
board_manager: {}

Expected behavior

I want to parse the result with JS, so I would expect a result that can be processed with:

JSON.parse(myOutput);

Environment

• CLI version (output of arduino-cli version):
  arduino-cli Version: nightly-83 Commit: bd20ce6
• OS and platform:
  macOS 10.14.6 (18G87)

Additional context

[masci]

This is fixed on master