test_runner: Remove unused type: ignore comments.

Also enable warn_unused_ignores.  I think the fact that there are so
few of these is good evidence that it’s not a significant burden for
people fixing type errors.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

mypy.ini

@@ -14,14 +14,11 @@ disallow_any_generics = True
 warn_no_return = True
 no_implicit_optional = True
 warn_redundant_casts = True
+warn_unused_ignores = True
 
 # Display the codes needed for # type: ignore[code] annotations.
 show_error_codes = True
 
-# It's useful to try this occasionally, and keep it clean; but when
-# someone fixes a type error we don't want to add a burden for them.
-#warn_unused_ignores = True
-
 # We use a lot of third-party libraries we don't have stubs for, as
 # well as a handful of our own modules that we haven't told mypy how
 # to find.  Ignore them.  (For some details, see:

zerver/lib/test_runner.py

@@ -152,8 +152,8 @@ class TextTestResult(runner.TextTestResult):
         self.failed_tests: List[str] = []
 
     def addInfo(self, test: TestCase, msg: str) -> None:
-        self.stream.write(msg)  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
-        self.stream.flush()  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
+        self.stream.write(msg)
+        self.stream.flush()
 
     def addInstrumentation(self, test: TestCase, data: Dict[str, Any]) -> None:
         append_instrumentation_data(data)
@@ -161,7 +161,7 @@ class TextTestResult(runner.TextTestResult):
     def startTest(self, test: TestCase) -> None:
         TestResult.startTest(self, test)
         self.stream.writeln(f"Running {full_test_name(test)}")  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
-        self.stream.flush()  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
+        self.stream.flush()
 
     def addSuccess(self, *args: Any, **kwargs: Any) -> None:
         TestResult.addSuccess(self, *args, **kwargs)
@@ -181,7 +181,7 @@ class TextTestResult(runner.TextTestResult):
         self.stream.writeln("** Skipping {}: {}".format(  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
             full_test_name(test),
             reason))
-        self.stream.flush()  # type: ignore[attr-defined] # https://github.com/python/typeshed/issues/3139
+        self.stream.flush()
 
 class RemoteTestResult(django_runner.RemoteTestResult):
     """