doctest: handle BdbQuit

Map `BdbQuit` exception to `outcomes.Exit`.

This is necessary since we are not wrapping `pdb.set_trace` there, and
therefore our `do_quit` is not called.

src/_pytest/doctest.py

@@ -1,4 +1,5 @@
 """ discover and run doctests in modules and test files."""
+import bdb
 import inspect
 import platform
 import sys
@@ -7,6 +8,7 @@ import warnings
 from contextlib import contextmanager
 
 import pytest
+from _pytest import outcomes
 from _pytest._code.code import ExceptionInfo
 from _pytest._code.code import ReprFileLocation
 from _pytest._code.code import TerminalRepr
@@ -155,6 +157,8 @@ def _init_runner_class():
         def report_unexpected_exception(self, out, test, example, exc_info):
             if isinstance(exc_info[1], Skipped):
                 raise exc_info[1]
+            if isinstance(exc_info[1], bdb.BdbQuit):
+                outcomes.exit("Quitting debugger")
             failure = doctest.UnexpectedException(test, example, exc_info)
             if self.continue_on_failure:
                 out.append(failure)

testing/test_pdb.py

@@ -458,7 +458,6 @@ class TestPDB:
     def test_pdb_interaction_doctest(self, testdir, monkeypatch):
         p1 = testdir.makepyfile(
             """
-            import pytest
             def function_1():
                 '''
                 >>> i = 0
@@ -477,9 +476,32 @@ class TestPDB:
 
         child.sendeof()
         rest = child.read().decode("utf8")
+        assert "! _pytest.outcomes.Exit: Quitting debugger !" in rest
+        assert "BdbQuit" not in rest
         assert "1 failed" in rest
         self.flush(child)
 
+    def test_doctest_set_trace_quit(self, testdir, monkeypatch):
+        p1 = testdir.makepyfile(
+            """
+            def function_1():
+                '''
+                >>> __import__('pdb').set_trace()
+                '''
+        """
+        )
+        # NOTE: does not use pytest.set_trace, but Python's patched pdb,
+        #       therefore "-s" is required.
+        child = testdir.spawn_pytest("--doctest-modules --pdb -s %s" % p1)
+        child.expect("Pdb")
+        child.sendline("q")
+        rest = child.read().decode("utf8")
+
+        assert "! _pytest.outcomes.Exit: Quitting debugger !" in rest
+        assert "= no tests ran in" in rest
+        assert "BdbQuit" not in rest
+        assert "UNEXPECTED EXCEPTION" not in rest
+
     def test_pdb_interaction_capturing_twice(self, testdir):
         p1 = testdir.makepyfile(
             """