Issue #21207: Detect when the os.urandom cached fd has been closed or replaced, and open it anew.
shallow defaults to 'True' not '1' (closes #21355)

Patch by Diana Clarke.
make operations on closed dumb databases raise a consistent exception (closes #19385)

Patch by Claudiu Popa.
#18243: Remove obsolete cautionary note from email mktime_tz docs.