Fix exit code for command line errors

Fixes #3913

AUTHORS

@@ -46,6 +46,7 @@ Christian Boelsen
 Christian Theunert
 Christian Tismer
 Christopher Gilling
+CrazyMerlyn
 Cyrus Maden
 Dhiren Serai
 Daniel Grana

changelog/3913.bugfix.rst

@@ -0,0 +1 @@
+Pytest now returns with correct exit code (EXIT_USAGEERROR, 4) when called with unknown arguments.

src/_pytest/config/argparsing.py

@@ -2,8 +2,13 @@ import six
 import warnings
 import argparse
 
+from gettext import gettext as _
+import sys as _sys
+
 import py
 
+from ..main import EXIT_USAGEERROR
+
 FILE_OR_DIR = "file_or_dir"
 
 
@@ -329,6 +334,16 @@ class MyOptionParser(argparse.ArgumentParser):
         # an usage error to provide more contextual information to the user
         self.extra_info = extra_info
 
+    def error(self, message):
+        """error(message: string)
+
+        Prints a usage message incorporating the message to stderr and
+        exits.
+        Overrides the method in parent class to change exit code"""
+        self.print_usage(_sys.stderr)
+        args = {"prog": self.prog, "message": message}
+        self.exit(EXIT_USAGEERROR, _("%(prog)s: error: %(message)s\n") % args)
+
     def parse_args(self, args=None, namespace=None):
         """allow splitting of positional arguments"""
         args, argv = self.parse_known_args(args, namespace)

testing/acceptance_test.py

@@ -1061,3 +1061,8 @@ def test_fixture_mock_integration(testdir):
     p = testdir.copy_example("acceptance/fixture_mock_integration.py")
     result = testdir.runpytest(p)
     result.stdout.fnmatch_lines("*1 passed*")
+
+
+def test_usage_error_code(testdir):
+    result = testdir.runpytest("-unknown-option-")
+    assert result.ret == EXIT_USAGEERROR