bpo-29778: Ensure python3.dll is loaded from correct locations when
Python is embedded (CVE-2020-15523).
bpo-41004: CVE-2020-14422: The __hash__() methods of ipaddress.IPv4Interface
and ipaddress.IPv6Interface incorrectly generated constant hash values
of 32 and 128 respectively. This resulted in always causing hash collisions.
The fix uses hash() to generate hash values for the tuple of (address, mask
length, network address).
bpo-39603: Prevent http header injection by rejecting control characters
in http.client.putrequest(...).