Issue 10556: test_zipimport_support implicitly imports too many modules (including _ssl) to safely clobber sys.modules after each test

second before epoch.  Original patch by Peter Wang, reported by Martin
Blais.

Fix readinst() if file.read(n) returns a bytes object longer than n:
return -1 instead of the the buffer size to raise an exception.
Simplify also the function code.

        scripts (implemented in #10679).

if available.

(at Georg's request)

Patch by Adreas Stührk.

This makes Header.encode throw a HeaderParseError if it winds up
formatting a header such that a continuation line has no leading
whitespace and looks like a header.  Since Header accepts values
containing newlines and preserves them (and this is by design), without
this fix any program that took user input (say, a subject in a web form)
and passed it to the email package as a header was vulnerable to header
injection attacks.  (As far as we know this has never been exploited.)

Thanks to Jakub Wilk for reporting this vulnerability.

in the operator module.