Warn about DerivedAge.txt for characters not yet in the pipeline (#668)

py/pipeline-workflow/check-draft-status.py

@@ -7,11 +7,40 @@
 with open("unicodetools/data/ucd/dev/DerivedAge.txt", 'r') as f:
     version = f.readline().strip().replace("# DerivedAge-", "").replace(".0.txt", "")
 
+PROVISIONALLY_ASSIGNED_AGE_NOTICE = f"""\
+While the Unicode Technical Committee has provisionally assigned these
+characters, they have not been accepted for Unicode {version}, nor for any
+specific version of Unicode.
+
+The Age property values for new characters are likely incorrect right
+now. They will be recomputed after the UTC accepts their encoding and
+this pull request is updated for the target version.
+""".replace("\n", "%0A")
+
+UNREVIEWED_AGE_NOTICE = f"""\
+These characters are neither accepted for Unicode {version}, nor for any
+specific version of Unicode, nor are they provisionally assigned.
+
+
+The Age property values for new characters are likely incorrect right
+now. They will be recomputed after the UTC accepts their encoding and
+this pull request is updated for the target version.
+""".replace("\n", "%0A")
+
 if pipeline_label != "pipeline-" + version:
     with open(os.environ['GITHUB_EVENT_PATH'], 'r') as f:
         event = json.load(f)
     print(event)
     draft = event['pull_request']['draft']
+    # Caution the reader that the Age values are placeholders.
+    if pipeline_label == "pipeline-provisionally-assigned":
+        print("::warning file=unicodetools/data/ucd/dev/DerivedAge.txt,"
+              f"title=Not in the {version} pipeline::" +
+              PROVISIONALLY_ASSIGNED_AGE_NOTICE)
+    else:  # Not even provisionally assigned.
+        print("::warning file=unicodetools/data/ucd/dev/DerivedAge.txt,"
+              f"title=Not in the {version} pipeline::" +
+              UNREVIEWED_AGE_NOTICE)
     if not draft:
         print("::error title=PR must be draft::"
               "PRs for character additions must be draft unless approved for "