Fix get_ts_synopsis catch-all triggered by bless trailer after PASS

[jasonb5]

Description

Fixes the master: ERROR Could not interpret CPRNC output message that has been appearing in TestStatus.log for passing baseline comparisons across entire integration suites.

Root cause

compare_baseline (CIME/hist_utils.py:592-598) appends a bless trailer after the PASS token emitted by _compare_hists:

Comparing hists for case '...'
  ...matched...
PASS
  Most recent bless: <sha>

get_ts_synopsis only handled the case where comments ended exactly with "PASS", so once any trailer was present the function fell through every recognized pattern and landed on the catch-all ERROR Could not interpret CPRNC output.

This became a near-universal symptom after #4952 (Preserve TestStatus and bless_log) added BLESS_LOG_NAME to the preserve list, so prior bless lines now persist across baseline regeneration and the trailer is appended on essentially every comparison.

Fix

Replace the brittle endswith("PASS") check with a single multiline regex that recognizes the verbatim PASS token regardless of where it sits in the comments and tolerates CRLF line endings without weakening the exact-match guarantee:

# Comparison passed if a line consisting of exactly "PASS" appears.
# _compare_hists writes this token verbatim; any other casing (Pass, pass,
# PASSING, ...) is not a status marker and must fall through. The optional
# \r tolerates CRLF line endings without weakening the exact-match check.
if re.search(r"^PASS\r?$", comments, re.MULTILINE):
    return ""

Tests

• New doctest in get_ts_synopsis covering the realistic production string 'Comparing hists\nPASS\n Most recent bless: sha:abc\n'.

• Four unit tests in CIME/tests/test_unit_hist_utils.py:

  • test_get_ts_synopsis_pass_at_end — PASS at end-of-string.
  • test_get_ts_synopsis_pass_on_own_line_with_multiple_lines_after — PASS followed by a bless trailer.
  • test_get_ts_synopsis_pass_is_case_sensitive_and_exact — pins that variants like Pass, pass, PASSING, passed, PASS, and PASS extra do NOT short-circuit.
  • test_get_ts_synopsis_pass_handles_crlf_line_endings — PASS on a CRLF-terminated line is recognized, both standalone and with a bless trailer.

• All hist_utils unit tests + doctests pass locally.

• Closes Still seeing "Could not interpret CPRNC output" in TestStatus.log #4932

Checklist

• My code follows the style guidelines of this project (black formatting)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that exercise my feature/fix and existing tests continue to pass
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding additions and changes to the documentation

[jgfouca]

Looks great! thanks