Print result of doctest failure

[niccokunzmann]

When the documentation tests fail, this change will print the result of that.
Before, there was no hint, now you can see this for example:

**********************************************************************
File "/home/nicco/icalendar/src/icalendar/tests/../../../docs/usage.rst", line 408, in usage.rst
Failed example:
    f.write(cal.to_ical())
Expected:
    733
Got:
    775
**********************************************************************
File "/home/nicco/icalendar/src/icalendar/tests/../../../docs/usage.rst", line 416, in usage.rst
Failed example:
    print(cal.to_ical().decode('utf-8')) # doctest: +NORMALIZE_WHITESPACE
Expected:
    BEGIN:VCALENDAR
    VERSION:2.0
    PRODID:-//My calendar product//mxm.dk//
    BEGIN:VEVENT
    SUMMARY:Python meeting about calendaring
    DTSTART:20050404T080000Z
    DTEND:20050404T100000Z
    DTSTAMP:20050404T001000Z
    UID:20050115T101010/27346262376@mxm.dk
    RRULE:FREQ=DAILY
    ATTENDEE;CN="Max Rasmussen";ROLE=REQ-PARTICIPANT:MAILTO:maxm@example.com
    ATTENDEE;CN="The Dude";ROLE=REQ-PARTICIPANT:MAILTO:the-dude@example.com
    LOCATION:Odense\, Denmark
    ORGANIZER;CN="Max Rasmussen";ROLE=CHAIR:MAILTO:noone@example.com
    PRIORITY:5
    BEGIN:VALARM
    ACTION:DISPLAY
    DESCRIPTION:Reminder: Event in 1 hour
    TRIGGER:-PT1H
    END:VALARM
    BEGIN:VALARM
    ACTION:DISPLAY
    DESCRIPTION:Reminder: Event in 24 hours
    TRIGGER:-P1D
    END:VALARM
    END:VEVENT
    END:VCALENDAR
    <BLANKLINE>
Got:
    BEGIN:VCALENDAR
    VERSION:2.0
    PRODID:-//My calendar product//mxm.dk//
    BEGIN:VEVENT
    SUMMARY:Python meeting about calendaring
    DTSTART:20050404T080000Z
    DTEND:20050404T100000Z
    DTSTAMP:20050404T001000Z
    UID:20050115T101010/27346262376@mxm.dk
    RRULE:FREQ=DAILY;INTERVAL=10
    RRULE:FREQ=DAILY;INTERVAL=10
    ATTENDEE;CN="Max Rasmussen";ROLE=REQ-PARTICIPANT:MAILTO:maxm@example.com
    ATTENDEE;CN="The Dude";ROLE=REQ-PARTICIPANT:MAILTO:the-dude@example.com
    LOCATION:Odense\, Denmark
    ORGANIZER;CN="Max Rasmussen";ROLE=CHAIR:MAILTO:noone@example.com
    PRIORITY:5
    BEGIN:VALARM
    ACTION:DISPLAY
    DESCRIPTION:Reminder: Event in 1 hour
    TRIGGER:-PT1H
    END:VALARM
    BEGIN:VALARM
    ACTION:DISPLAY
    DESCRIPTION:Reminder: Event in 24 hours
    TRIGGER:-P1D
    END:VALARM
    END:VEVENT
    END:VCALENDAR
**********************************************************************
1 items had failures:
   2 of  89 in usage.rst
***Test Failed*** 2 failures.

[coveralls]

Pull Request Test Coverage Report for Build 12449054289

Details

• 4 of 4 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 96.372%

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Totals
Change from base Build 12336865356:	0.02%
Covered Lines:	4580
Relevant Lines:	4747

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💛 - Coveralls

[stevepiercy]

Nice improvement