unittest: assertRaises() with an instance instead of a type

[Terry Reedy]

I can't find any HTML in what I posted, so HTML is not the problem. A
difference could be the content type. I had in my posting:

Content-Type: text/plain; charset=ISO-8859-15; format=flowed

Another one titled "Pipelining in Python", where TB doesn't mess up the
formatting, has:

Content-Type: text/plain; charset=ISO-8859-1

Searching the web turned up [1], the gist is that "format=flowed" means
that your mailer is allowed to move linebreaks and quotation signs (">
") as it wants. Which is not what I meant. Some more search turned up
[2], which tells us how to disable this. Go to the settings, advanced
section and find the button that fires up the raw configuration editor.
There, locate the key mailnews.send_plaintext_flowed and change the
according value to false.

# Checking...
if this.worked:
hurray("I didn't even have to close the message in writing")

Looks great!
I never knew about that setting.