get-poetry.py works, but install-poetry fails with certificate errors on Ubuntu 20.04 LTS

Hi,

I'm behind a corporate SSL-inspecting firewall with our own certificates.
I have them installed properly on my machine (with update-ca-certificates).
cURL works on HTTPS sites, and installing poetry via get-poetry.py works.
However, trying to install it via the newer install-poetry throws SSL errors:

WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))': /simple/poetry/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))': /simple/poetry/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))': /simple/poetry/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))': /simple/poetry/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))': /simple/poetry/
Could not fetch URL https://pypi.org/simple/poetry/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/poetry/ (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))) - skipping
ERROR: Could not find a version that satisfies the requirement poetry==1.1.13 (from versions: none)
ERROR: No matching distribution found for poetry==1.1.13
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1131)'))) - skipping
WARNING: There was an error checking the latest version of pip.

I set the certificate folder to REQUESTS_CA_BUNDLE (although I don't think requests is being used)
I even added our certificates to the certifi cert bundle file, but no luck...
This one has me completely stumped, since get-poetry works fine and both seem to use urllib...
Corporate SSL inspection is such a PITA for python...

Compare the newer install-poetry script with get-poetry.py and reproduce the certificate failure on Ubuntu 20.04 behind a corporate SSL-inspecting firewall. Investigate how the installer and its package downloads use local certificate configuration; done means installation succeeds with the machine's trusted certificates.