test: blocked-check 用 _req_safe 替代 _req 避免 API 错误误判 - Closes #58

- 新增 _req_safe()：API 错误返回 None 而非 sys.exit(1)
- blocked_check / _unblock_issues_blocked_by / _get_blocking_refs 改用 _req_safe
- API 失败时保守处理：保持 blocked 状态（不误解除）
- 验证：#18 正确识别被 #57 阻塞

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/agent_poller.py

@@ -56,6 +56,27 @@ def _req(method, path, data=None):
         sys.exit(1)
 
 
+def _req_safe(method, path, data=None):
+    """Like _req but returns None on HTTPError instead of crashing.
+    Used for probing issue/PR existence where the caller can handle absence.
+    """
+    url = f"{BASE}{path}"
+    payload = json.dumps(data).encode("utf-8") if data else None
+    req = urllib.request.Request(url, data=payload, method=method)
+    req.add_header("Authorization", f"token {GITEA_TOKEN}")
+    req.add_header("Content-Type", "application/json")
+    try:
+        with urllib.request.urlopen(req) as resp:
+            raw = resp.read()
+            if not raw:
+                return {}
+            return json.loads(raw)
+    except urllib.error.HTTPError as e:
+        body = e.read().decode()
+        print(f"API Error {e.code}: {body}", file=sys.stderr)
+        return None
+
+
 # ── Issue operations ─────────────────────────────────────────────────────────
 
 def list_issues(labels: list[str] | None = None):
@@ -82,17 +103,17 @@ def _get_blocking_refs(issue_num: int) -> set[int]:
     """
     refs: set[int] = set()
     # Body
-    issue = _req("GET", f"/issues/{issue_num}")
+    issue = _req_safe("GET", f"/issues/{issue_num}")
+    if issue is None:
+        return refs  # API error → return empty set, keep blocked
     body = issue.get("body", "") or ""
     refs.update(int(m.group(1)) for m in re.finditer(r'#(\d+)', body))
     # Comments
-    try:
-        comments = _req("GET", f"/issues/{issue_num}/comments")
+    comments = _req_safe("GET", f"/issues/{issue_num}/comments")
+    if comments:
         for c in comments:
             cbody = c.get("body", "") or ""
             refs.update(int(m.group(1)) for m in re.finditer(r'#(\d+)', cbody))
-    except SystemExit:
-        pass
     return refs
 
 
@@ -119,13 +140,13 @@ def blocked_check():
 
         all_resolved = True
         for blk in blocking_nums:
-            try:
-                blk_issue = _req("GET", f"/issues/{blk}")
+            blk_issue = _req_safe("GET", f"/issues/{blk}")
+            if blk_issue is None:
+                all_resolved = False  # API error → keep blocked
+                break
             if blk_issue.get("state") != "closed":
                 all_resolved = False
                 break
-            except SystemExit:
-                pass
 
         if all_resolved:
             current_label_names = [l["name"] for l in issue.get("labels", [])]
@@ -179,10 +200,7 @@ def _unblock_issues_blocked_by(closed_num):
     in any blocked issue and all referenced issues are now closed,
     removes the 'blocked' label and comments on the unblocked issue.
     """
-    try:
-        all_blocked = _req("GET", "/issues?state=open&labels=blocked")
-    except SystemExit:
-        return
+    all_blocked = _req_safe("GET", "/issues?state=open&labels=blocked")
     if not all_blocked:
         return
 
@@ -196,13 +214,13 @@ def _unblock_issues_blocked_by(closed_num):
         for blk in blocking_nums:
             if blk == closed_num:
                 continue
-            try:
-                blk_issue = _req("GET", f"/issues/{blk}")
+            blk_issue = _req_safe("GET", f"/issues/{blk}")
+            if blk_issue is None:
+                all_resolved = False  # API error → keep blocked
+                break
             if blk_issue.get("state") != "closed":
                 all_resolved = False
                 break
-            except SystemExit:
-                pass  # Inaccessible → treat as resolved
 
         if all_resolved:
             current_label_names = [l["name"] for l in issue.get("labels", [])]