Bug in example code for Embedding page in Boost.Python tutorial

Hi all,

on page https://www.boost.org/doc/libs/1_75_0/libs/python/doc/html/tutorial/tutorial/embedding.html there is a bug in the example code.

The line
object ignored = exec("hello = file('hello.txt', 'w')\n"
will cause an error_already_set exception (using Python 3.7 on Windows 10).

The line should read
object ignored = exec("hello = open('hello.txt', 'w+')\n"

Best regards