"http://" missing from environment variable values

[mebble]

http:// is missing from environment variable values

$ env | grep -i proxy
HTTPS_PROXY=172.31.2.4:8080/
ftp_proxy=ftp://172.31.2.4:8080/
FTP_PROXY=ftp://172.31.2.4:8080/
no_proxy=localhost,127.0.0.1,192.168.1.1,::1,*.local
https_proxy=172.31.2.4:8080/
HTTP_PROXY=http://172.31.2.4:8080/
NO_PROXY=localhost,127.0.0.1,192.168.1.1,::1,*.local
http_proxy=http://172.31.2.4:8080/
rsync_proxy=rsync://172.31.2.4:8080/
RSYNC_PROXY=rsync://172.31.2.4:8080/

As you can see above, when setting the proxy through proxyman, the HTTPS_PROXY and https_proxy variables don't have the http:// prefix which ends up breaking pip install:

raise ProxySchemeUnknown(proxy.scheme)
urllib3.exceptions.ProxySchemeUnknown: Not supported proxy scheme 172.31.2.4

Ubuntu 18.04 Proxyman v3.1.2 zsh 5.4.2 (x86_64-ubuntu-linux-gnu)