Trac #30589: Upgrade Python to 3.9.1, pip to 20.3.3

This contains the upgrade to Python 3.9.1

To test, use
{{{
./configure --without-system-python3 --enable-download-from-upstream-url
}}}

URL: https://trac.sagemath.org/30589
Reported by: mkoeppe
Ticket author(s): Matthias Koeppe
Reviewer(s): John Palmieri, Samuel Lelièvre

build/pkgs/pip/checksums.ini

@@ -1,5 +1,5 @@
 tarball=pip-VERSION.tar.gz
-sha1=5e708de15d0959386595bea819d75fbc5d4480b3
-md5=efd9dc5c7405452c72c0e3cd410a2018
-cksum=3748660343
+sha1=a8c85abfdc0bf15dd7360865f59e4234be00d1e2
+md5=3d5d0639042c829bba411d3735267546
+cksum=4219824548
 upstream_url=https://pypi.io/packages/source/p/pip/pip-VERSION.tar.gz

build/pkgs/pip/package-version.txt

@@ -1 +1 @@
-20.2.3
+20.3.3

build/pkgs/python3/checksums.ini

@@ -1,5 +1,5 @@
 tarball=Python-VERSION.tar.xz
-sha1=68d6c7f948801cc755905162f5ee7589595edee4
-md5=35b5a3d0254c1c59be9736373d429db7
-cksum=2309344767
+sha1=77f4105846f6740297e50d7535a42c02d6b8e7db
+md5=61981498e75ac8f00adcb908281fadb6
+cksum=4032849512
 upstream_url=https://www.python.org/ftp/python/VERSION/Python-VERSION.tar.xz

build/pkgs/python3/package-version.txt

@@ -1 +1 @@
-3.8.5
+3.9.1