Line numbers don't match code lines

[lgarcin]

The lines in the output of .. runblock:: pycon are too small. When use with the :linenos: flag, the line numbers don't match code lines.

For example

.. runblock:: pycon
    :linenos:

    >>> a = (1, 'a', 2, 'b', 3, 'c', 4, 'd', 5, 'e', 6, 'f')
    >>> a[3]
    >>> a[2:]
    >>> a[:5]
    >>> a[-3]
    >>> a[2:9:2]
    >>> a[8:1:-3]

produces

[WhyNotHugo]

I don't think this can trivially fixed: this sphinx extension just generates the block, and the line numbers are later added by sphinx. We've no control over line numbers, so there's not much we can do on our end.