Fix SSL cert verification failures behind enterprise inspection proxies

[edurdevic]

Problem

ucode init fails with CERTIFICATE_VERIFY_FAILED: self-signed certificate in certificate chain on networks with a corporate TLS inspection proxy, even though curl to the same AI Gateway endpoint succeeds.

Root cause: Python's urllib.request.urlopen does not load the OS trust store on all platforms. The proxy injects a self-signed CA that curl finds via the system keychain, but Python's default SSL context misses it. The error surfaces as:

Databricks Unity AI Gateway probe failed on this workspace
(network error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed:
self-signed certificate in certificate chain (ssl.c:1001)).

Fix

Add _make_ssl_context() in databricks.py that creates a default SSL context and additionally loads any CA bundle pointed to by REQUESTS_CA_BUNDLE, CURL_CA_BUNDLE, or SSL_CERT_FILE — the same env vars honored by curl and the requests library. All three urlopen call sites (_http_get_json, _http_post_json, discover_sql_warehouse_http_path) now use this context.

Workaround for affected customers (before this ships)

export REQUESTS_CA_BUNDLE=/path/to/enterprise-ca.pem
ucode init

Test plan

• All existing unit tests pass (uv run pytest)
• Lint clean (uv run ruff check . + uv run ruff format --check)
• Manual test on a workspace behind an SSL inspection proxy

This pull request and its description were written by Isaac.

[rohita5l]

Bug — break fires even when load_verify_locations fails (_make_ssl_context, line ~214)

          try:
              ctx.load_verify_locations(cafile=ca_bundle)
          except ssl.SSLError:
              pass
          break   # ← outside try/except, always executes

[rohita5l]

Minor — _make_ssl_context() called on every request, should be cached

It hits the env vars + filesystem on every urlopen call. The rest of the file already uses @functools.cache for this pattern. Adding @functools.cache makes it a one-shot per process.

[rohita5l]

OSError (e.g. permission denied) is not caught here — Path.is_file() returns True for files the current user cannot read, but load_verify_locations will then raise OSError: Permission denied, which propagates uncaught and crashes the process.

Suggest broadening the except catch