Fix test_http.request_callback

[ddelange]

Title

Fix tests with urllib3 v2

Motivation

Fix #784, CI was running only 3.7 (hence urllib3 v1) due to a typo regarding python-version.

Tests

Fix sftp tests now that CI is running python 3.8--3.12

Work in progress

Checklist

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Workflow

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[ddelange]

with the new python versions in the test matrix, ssl in integration test started complaining about ftps server's self-signed cert

ssl.SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate (_ssl.c:1131)

so i explicitly created a self-signed cert for localhost and passed it in the integration test. but now there's

ERROR    smart_open.ftp:ftp.py:96 Unable to connect to FTP server: try checking the host and port!

and i'm not sure how to proceed.

[ddelange]

~@RachitSharma2001 as author of these files, do you have any idea?~

[ddelange]

got it, we're green now:)

  rsa_cert_file=/etc/vsftpd.pem
+ rsa_private_key_file=/etc/vsftpd.key

[ddelange]

@mpenkov please review

[mpenkov]

LGTM, thank you!