Require Python 3.12+ (Python 3.10/3.11 hang on macOS 15 during corpus download)

[janhoy]

Problem

On macOS 15 (Darwin 25.4.0), running Solr Orbit with Python 3.10 or 3.11 causes the benchmark to hang indefinitely at ~200% CPU during the first corpus download (when the local data cache is empty).

Root Cause

Python 3.10/3.11 has a bug triggered by macOS 15's high-precision nanosecond filesystem timestamps. When os.stat() is called on any recently-created file, the fill_time() function in CPython's posixmodule.c converts the nanosecond timestamp using PyNumber_Multiply. For large nanosecond values, this triggers Karatsuba big-integer multiplication (k_mul), which calls _PyErr_CheckSignalsTstate. If a Python signal handler is active at that moment, it executes Python bytecode that calls os.stat() again — creating infinite recursion at ~200% CPU.

This was discovered by profiling the hung process with sample, which showed:

os_stat → fill_time → PyNumber_Multiply → k_mul → _PyErr_CheckSignalsTstate
  → (Python signal handler) → os_stat → fill_time → ... (infinite recursion)

The hang affects urllib3/SSL corpus downloads. It does not affect runs where corpus data is already cached.

Fix

Upgrade to Python 3.12+, which does not exhibit this behavior.

Suggested Changes

• Update .python-version to 3.12.x
• Update supported_python_versions in setup.py to start from (3, 12)
• Update check_python_version() in osbenchmark/__init__.py to require >= 3.12
• Update tox.ini to drop py310 and py311 environments
• Update DEVELOPER_GUIDE.md prerequisite to "Python 3.12+" with a note about the macOS 15 issue