Log API Calls and the Rate Limit Left on Each macOS Admission Check

The calls per check grow with the number of active runs, and the token's
hourly limit is shared by the whole repository, so each check now logs how
many calls it made and what the last response says is left.

scripts/tests/test_ci_macos_admission.py

@@ -9,6 +9,7 @@ import os
 import sys
 import unittest
 import urllib.error
+from unittest import mock
 
 sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
 
@@ -289,6 +290,41 @@ class MeasureTest(unittest.TestCase):
         self.assertFalse(any("event" in params for _, params in api.calls))
 
 
+class ApiTest(unittest.TestCase):
+    class Response:
+        def __init__(self, headers):
+            self.headers = headers
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *_):
+            return False
+
+        def read(self):
+            return b"{}"
+
+    def test_reports_calls_and_the_rate_limit_left(self):
+        api = admission.Api("token")
+        responses = [self.Response({}),
+                     self.Response({"X-RateLimit-Remaining": "812", "X-RateLimit-Limit": "1000"})]
+        with mock.patch.object(admission.urllib.request, "urlopen", side_effect=responses):
+            api.get("first")
+            calls_before = api.calls
+            api.get("second")
+        self.assertEqual(api.usage(0), "  API calls this check: 2, rate limit left: 812 of 1000")
+        self.assertEqual(api.usage(calls_before), "  API calls this check: 1, rate limit left: 812 of 1000")
+
+    def test_reads_the_rate_limit_from_a_failed_request(self):
+        api = admission.Api("token")
+        headers = {"X-RateLimit-Remaining": "0", "X-RateLimit-Limit": "1000"}
+        error = urllib.error.HTTPError("url", 403, "Forbidden", headers, None)
+        with mock.patch.object(admission.urllib.request, "urlopen", side_effect=error), \
+             self.assertRaises(urllib.error.HTTPError):
+            api.get("runs")
+        self.assertEqual(api.usage(0), "  API calls this check: 1, rate limit left: 0 of 1000")
+
+
 class WaitTest(unittest.TestCase):
     def run_wait(self, results, limit=5, wait_minutes=60, poll_seconds=120):
         results = iter(results)