azure-job.yml: Use python -u

azure-job.yml

@@ -32,5 +32,5 @@ jobs:
       - script: pip install -r requirements-ci.txt
         displayName: Install CI requirements
 
-      - script: PYTHONUNBUFFERED=1 pytest
+      - script: python -u -m pytest
         displayName: Run pytest (Python ${{ python.value.spec }})

conftest.py

@@ -36,6 +36,23 @@
 from stdio_mgr import stdio_mgr
 
 
+# is_stdout_buffered is copied from https://stackoverflow.com/a/49736559
+# Licensed CC-BY-SA 4.0
+# Author https://stackoverflow.com/users/528711/sparrowt
+def is_stdout_buffered():
+    # Print a single space + carriage return but no new-line
+    # (should have no visible effect)
+    print(" \r")
+    # If the file position is a positive integer then stdout is buffered
+    try:
+        pos = sys.stdout.tell()
+        if pos > 0:
+            return True
+    except IOError:  # In some terminals tell() throws IOError if stdout is unbuffered
+        pass
+    return False
+
+
 @pytest.fixture(scope="session")
 def warnings_are_errors(pytestconfig):
     """Provide concise access to '-W error::Warning' CLI option."""
@@ -76,7 +93,7 @@ def enable_warnings_plugin(request):
 @pytest.fixture(scope="session")
 def unbufferedio():
     """Provide concise access to PYTHONUNBUFFERED envvar."""
-    return os.environ.get("PYTHONUNBUFFERED")
+    return os.environ.get("PYTHONUNBUFFERED") or not is_stdout_buffered()
 
 
 @pytest.fixture(autouse=True)