Pip installs using CircleCI docker image needs proxy server

I use the Docker image circleci/python:3.8.2-browsers. I spool up a Python 3.8.2 virtual environment, and then install a bunch of Python packages using pip install -r requirements.txt.

While running the installs, there are lots of warnings logged like the below:

WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d0f520>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d0f040>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d0f730>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d0f820>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d0f910>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask/
Requirement already up-to-date: Flask==1.1.2 in ./venv/lib/python3.8/site-packages (from -r requirements.txt (line 5)) (1.1.2)
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d08be0>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask-socketio/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d08a30>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask-socketio/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d08520>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask-socketio/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d085b0>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask-socketio/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7f4c39d08310>: Failed to establish a new connection: [Errno -2] Name or service not known')': /flask-socketio/
Requirement already up-to-date: Flask-SocketIO==4.3.0 in ./venv/lib/python3.8/site-packages (from -r requirements.txt (line 6)) (4.3.0

The solution (per this comment) seems to be to use a proxy.

pip install flask --proxy=“my_proxy_name:port”

How can I set up a proxy via CircleCI config.yml? Can you point me in the right direction?