change flask logs from stdout' code example

Example 1: flask console log

from __future__ import print_function # In python 2.7
import sys

@app.route('/button/')
def button_clicked():
    print('Hello world!', file=sys.stderr)
    return redirect('/')

Example 2: flask print to console

import sys

print('This is error output', file=sys.stderr)
print('This is standard output', file=sys.stdout)