fix download folder having spaces being read as separate cmds

[shubham3121]

Description

Please include a summary of the change, the motivation, and any additional context that will help others understand your PR. If it closes one or more open issues, please tag them as described here.

Affected Dependencies

Fixes: https://github.com/OpenMined/PySyft/issues/6717

• fix download folder having spaces being read as separate cmds
• print the command to start the virtualenv where quickstart is installed

How has this been tested?

• Describe the tests that you ran to verify your changes.
• Provide instructions so we can reproduce.
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Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [x] I have commented my code following the OpenMined Styleguide
• [x] I have labeled this PR with the relevant Type labels
• [x] My changes are covered by tests