Fix error message on IOError

Author: Rémi Lapeyre

Lib/json/tool.py

@@ -36,7 +36,10 @@ def main():
         except ValueError as e:
             raise SystemExit(e)
 
-    outfile = sys.stdout if options.outfile == '-' else open(options.outfile, 'w')
+    try:
+        outfile = sys.stdout if options.outfile == '-' else open(options.outfile, 'w')
+    except IOError as e:
+        parser.error("can't open '{}': {}".format(options.outfile, str(e)))
     with outfile:
         json.dump(obj, outfile, sort_keys=sort_keys, indent=4)
         outfile.write('\n')

Lib/test/test_json/test_tool.py

@@ -4,7 +4,7 @@
 import unittest
 from subprocess import Popen, PIPE
 from test import support
-from test.support.script_helper import assert_python_ok
+from test.support.script_helper import assert_python_ok, assert_python_failure
 
 
 class TestTool(unittest.TestCase):
@@ -99,6 +99,15 @@ def test_infile_same_outfile(self):
         self.assertEqual(out, b'')
         self.assertEqual(err, b'')
 
+    def test_unavailable_outfile(self):
+        infile = self._create_infile()
+        rc, out, err = assert_python_failure('-m', 'json.tool', infile, '/bla/outfile')
+        self.assertEqual(rc, 2)
+        self.assertEqual(out, b'')
+        err = err.decode().splitlines()
+        self.assertEqual(err[0], 'usage: python -m json.tool [-h] [--sort-keys] [infile] [outfile]')
+        self.assertEqual(err[1], "python -m json.tool: error: can't open '/bla/outfile': [Errno 2] No such file or directory: '/bla/outfile'")
+
     def test_help_flag(self):
         rc, out, err = assert_python_ok('-m', 'json.tool', '-h')
         self.assertEqual(rc, 0)