Certificate expired for www2.graphviz.org
$ LANG=C wget https://www2.graphviz.org/Packages/stable/portable_source/graphviz-2.44.1.tar.gz
--2020-09-08 06:03:53-- https://www2.graphviz.org/Packages/stable/portable_source/graphviz-2.44.1.tar.gz
Resolving www2.graphviz.org (www2.graphviz.org)... 147.28.0.22
Connecting to www2.graphviz.org (www2.graphviz.org)|147.28.0.22|:443... connected.
ERROR: cannot verify www2.graphviz.org's certificate, issued by 'CN=Let\'s Encrypt Authority X3,O=Let\'s Encrypt,C=US':
Issued certificate has expired.
To connect to www2.graphviz.org insecurely, use `--no-check-certificate'.