Make PytestWarning and RemovedInPytest4Warning part of the public API

src/_pytest/config/__init__.py

@@ -176,9 +176,9 @@ def _prepareconfig(args=None, plugins=None):
                 else:
                     pluginmanager.register(plugin)
         if warning:
-            from _pytest.warning_types import PytestUsageWarning
+            from _pytest.warning_types import PytestWarning
 
-            warnings.warn(warning, PytestUsageWarning)
+            warnings.warn(warning, PytestWarning)
         return pluginmanager.hook.pytest_cmdline_parse(
             pluginmanager=pluginmanager, args=args
         )

src/_pytest/python.py

@@ -44,11 +44,7 @@ from _pytest.mark.structures import (
     get_unpacked_marks,
     normalize_mark_list,
 )
-from _pytest.warning_types import (
-    PytestUsageWarning,
-    RemovedInPytest4Warning,
-    PytestWarning,
-)
+from _pytest.warning_types import RemovedInPytest4Warning, PytestWarning
 
 # relative paths that we use to filter traceback entries from appearing to the user;
 # see filter_traceback
@@ -671,12 +667,12 @@ class Class(PyCollector):
             self.std_warn(
                 "cannot collect test class %r because it has a "
                 "__init__ constructor" % self.obj.__name__,
-                PytestUsageWarning,
+                PytestWarning,
             )
             return []
         elif hasnew(self.obj):
             self.std_warn(
-                PytestUsageWarning(
+                PytestWarning(
                     "cannot collect test class %r because it has a "
                     "__new__ constructor" % self.obj.__name__
                 )

src/_pytest/warning_types.py

@@ -2,9 +2,5 @@ class PytestWarning(UserWarning):
     """Base class for all warnings emitted by pytest"""
 
 
-class PytestUsageWarning(PytestWarning):
-    """Warnings related to pytest usage: either command line or testing code."""
-
-
 class RemovedInPytest4Warning(PytestWarning, DeprecationWarning):
     """warning class for features that will be removed in pytest 4.0"""

src/pytest.py

@@ -19,45 +19,47 @@ from _pytest.main import Session
 from _pytest.nodes import Item, Collector, File
 from _pytest.fixtures import fillfixtures as _fillfuncargs
 from _pytest.python import Package, Module, Class, Instance, Function, Generator
-
 from _pytest.python_api import approx, raises
+from _pytest.warning_types import PytestWarning, RemovedInPytest4Warning
 
 set_trace = __pytestPDB.set_trace
 
 __all__ = [
-    "main",
-    "UsageError",
-    "cmdline",
-    "hookspec",
-    "hookimpl",
     "__version__",
-    "register_assert_rewrite",
-    "freeze_includes",
-    "set_trace",
-    "warns",
-    "deprecated_call",
-    "fixture",
-    "yield_fixture",
-    "fail",
-    "skip",
-    "xfail",
-    "importorskip",
-    "exit",
-    "mark",
-    "param",
-    "approx",
     "_fillfuncargs",
-    "Item",
-    "File",
-    "Collector",
-    "Package",
-    "Session",
-    "Module",
+    "approx",
     "Class",
-    "Instance",
+    "cmdline",
+    "Collector",
+    "deprecated_call",
+    "exit",
+    "fail",
+    "File",
+    "fixture",
+    "freeze_includes",
     "Function",
     "Generator",
+    "hookimpl",
+    "hookspec",
+    "importorskip",
+    "Instance",
+    "Item",
+    "main",
+    "mark",
+    "Module",
+    "Package",
+    "param",
+    "PytestWarning",
     "raises",
+    "register_assert_rewrite",
+    "RemovedInPytest4Warning",
+    "Session",
+    "set_trace",
+    "skip",
+    "UsageError",
+    "warns",
+    "xfail",
+    "yield_fixture",
 ]
 
 if __name__ == "__main__":

testing/test_assertrewrite.py

@@ -761,9 +761,8 @@ def test_rewritten():
 
     def test_rewrite_warning(self, pytestconfig):
         hook = AssertionRewritingHook(pytestconfig)
-        from _pytest.warning_types import PytestWarning
 
-        with pytest.warns(PytestWarning):
+        with pytest.warns(pytest.PytestWarning):
             hook.mark_rewrite("_pytest")
 
     def test_rewrite_module_imported_from_conftest(self, testdir):

testing/test_mark.py

@@ -16,7 +16,7 @@ from _pytest.mark import (
 from _pytest.nodes import Node
 
 ignore_markinfo = pytest.mark.filterwarnings(
-    "ignore:MarkInfo objects:_pytest.warning_types.RemovedInPytest4Warning"
+    "ignore:MarkInfo objects:pytest.RemovedInPytest4Warning"
 )
 
 

tox.ini

@@ -218,9 +218,9 @@ norecursedirs = .tox ja .hg cx_freeze_source testing/example_scripts
 xfail_strict=true
 filterwarnings =
     error
-    ignore:yield tests are deprecated, and scheduled to be removed in pytest 4.0:
-    ignore:Metafunc.addcall is deprecated and scheduled to be removed in pytest 4.0:
-    ignore:Module already imported so cannot be rewritten:
+    ignore:yield tests are deprecated, and scheduled to be removed in pytest 4.0:pytest.RemovedInPytest4Warning
+    ignore:Metafunc.addcall is deprecated and scheduled to be removed in pytest 4.0:pytest.RemovedInPytest4Warning
+    ignore:Module already imported so cannot be rewritten:pytest.PytestWarning
     # produced by path.local
     ignore:bad escape.*:DeprecationWarning:re
     # produced by path.readlines