Add support for installation of bench on linux mint

[gunic0rn]

Issue: Easy Install
Running the install script on linux mint fails

Do the checklist before filing an issue:

• Did you retain the logfile (path of logfile is shared while the script is run)? We definitely need the logfile to debug any easy install related issues.
• Is this something you can debug and fix? Send a pull request! Bug fixes and documentation fixes are welcome

Distro Information (Required)

1. uname -a
   Linux gunic0rn 5.8.0-45-generic frappe/bench#51~20.04.1-Ubuntu SMP Tue Feb 23 13:46:31 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

2. cat /etc/*-release

DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=20.1
DISTRIB_CODENAME=ulyssa
DISTRIB_DESCRIPTION="Linux Mint 20.1 Ulyssa"
NAME="Linux Mint"
VERSION="20.1 (Ulyssa)"
ID=linuxmint
ID_LIKE=ubuntu
PRETTY_NAME="Linux Mint 20.1"
VERSION_ID="20.1"
HOME_URL="https://www.linuxmint.com/"
SUPPORT_URL="https://forums.linuxmint.com/"
BUG_REPORT_URL="http://linuxmint-troubleshooting-guide.readthedocs.io/en/latest/"
PRIVACY_POLICY_URL="https://www.linuxmint.com/"
VERSION_CODENAME=ulyssa
UBUNTU_CODENAME=focal

Command Run (Required)

  sudo python3 install.py --production

Log File (Required)

Logs are saved under /tmp/logs/easy-install__2021-03-18__16-20.log
curl already installed!
wget already installed!
git already installed!
pip3 already installed!
ERROR: launchpadlib 1.10.13 requires testresources, which is not installed.
pip3 already installed!
Checking System Compatibility...
Sorry, the installer doesn't support linux mint. Aborting installation!

Screenshots

Additional context

Possible Solution

This is a simple issue, that can be solved by adding linux mint to the list of supported environments and distributions.
'linux mint': [19, 20]

[gavindsouza]

Can you respond to my query on your PR so that we can resolve this ASAP?