Avoid “error: None” messages from distutils (#4931).

Thanks to Amaury Forgeot d’Arc and Philip J. Eby.

Doc/distutils/apiref.rst

@@ -1171,15 +1171,6 @@ other utility module.
    underscore. No { } or ( ) style quoting is available.
 
 
-.. function:: grok_environment_error(exc[, prefix='error: '])
-
-   Generate a useful error message from an :exc:`OSError` exception object.
-   Handles Python 1.5.1 and later styles, and does what it can to deal with
-   exception objects that don't have a filename (which happens when the error
-   is due to a two-file operation, such as :func:`~os.rename` or :func:`~os.link`).
-   Returns the error message as a string prefixed with *prefix*.
-
-
 .. function:: split_quoted(s)
 
    Split a string up according to Unix shell-like rules for quotes and backslashes.

Lib/distutils/core.py

@@ -11,7 +11,6 @@ import sys
 
 from distutils.debug import DEBUG
 from distutils.errors import *
-from distutils.util import grok_environment_error
 
 # Mainly import these so setup scripts can "from distutils.core import" them.
 from distutils.dist import Distribution
@@ -149,13 +148,11 @@ def setup (**attrs):
         except KeyboardInterrupt:
             raise SystemExit("interrupted")
         except (IOError, os.error) as exc:
-            error = grok_environment_error(exc)
-
             if DEBUG:
-                sys.stderr.write(error + "\n")
+                sys.stderr.write("error: %s\n" % (exc,))
                 raise
             else:
-                raise SystemExit(error)
+                raise SystemExit("error: %s" % (exc,))
 
         except (DistutilsError,
                 CCompilerError) as msg:

Lib/distutils/dir_util.py

@@ -2,7 +2,7 @@
 
 Utility functions for manipulating directories and directory trees."""
 
-import os, sys
+import os
 import errno
 from distutils.errors import DistutilsFileError, DistutilsInternalError
 from distutils import log
@@ -182,7 +182,6 @@ def remove_tree(directory, verbose=1, dry_run=0):
     Any errors are ignored (apart from being reported to stdout if 'verbose'
     is true).
     """
-    from distutils.util import grok_environment_error
     global _path_created
 
     if verbose >= 1:
@@ -199,8 +198,7 @@ def remove_tree(directory, verbose=1, dry_run=0):
             if abspath in _path_created:
                 del _path_created[abspath]
         except (IOError, OSError) as exc:
-            log.warn(grok_environment_error(
-                    exc, "error removing %s: " % directory))
+            log.warn("error removing %s: %s", directory, exc)
 
 def ensure_relative(path):
     """Take the full path 'path', and make it a relative path.

Lib/distutils/tests/test_util.py

@@ -8,7 +8,8 @@ from test.support import run_unittest
 from distutils.errors import DistutilsPlatformError, DistutilsByteCompileError
 from distutils.util import (get_platform, convert_path, change_root,
                             check_environ, split_quoted, strtobool,
-                            rfc822_escape, byte_compile)
+                            rfc822_escape, byte_compile,
+                            grok_environment_error)
 from distutils import util # used to patch _environ_checked
 from distutils.sysconfig import get_config_vars
 from distutils import sysconfig
@@ -285,6 +286,13 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
         finally:
             sys.dont_write_bytecode = old_dont_write_bytecode
 
+    def test_grok_environment_error(self):
+        # test obsolete function to ensure backward compat (#4931)
+        exc = IOError("Unable to find batch file")
+        msg = grok_environment_error(exc)
+        self.assertEqual(msg, "error: Unable to find batch file")
+
+
 def test_suite():
     return unittest.makeSuite(UtilTestCase)
 

Lib/distutils/util.py

@@ -213,25 +213,10 @@ def subst_vars (s, local_vars):
 
 
 def grok_environment_error (exc, prefix="error: "):
-    """Generate a useful error message from an EnvironmentError (IOError or
-    OSError) exception object.  Handles Python 1.5.1 and 1.5.2 styles, and
-    does what it can to deal with exception objects that don't have a
-    filename (which happens when the error is due to a two-file operation,
-    such as 'rename()' or 'link()'.  Returns the error message as a string
-    prefixed with 'prefix'.
-    """
-    # check for Python 1.5.2-style {IO,OS}Error exception objects
-    if hasattr(exc, 'filename') and hasattr(exc, 'strerror'):
-        if exc.filename:
-            error = prefix + "%s: %s" % (exc.filename, exc.strerror)
-        else:
-            # two-argument functions in posix module don't
-            # include the filename in the exception object!
-            error = prefix + "%s" % exc.strerror
-    else:
-        error = prefix + str(exc.args[-1])
-
-    return error
+    # Function kept for backward compatibility.
+    # Used to try clever things with EnvironmentErrors,
+    # but nowadays str(exception) produces good messages.
+    return prefix + str(exc)
 
 
 # Needed by 'split_quoted()'

Misc/NEWS

@@ -16,6 +16,9 @@ Library
 - Issue #20875: Prevent possible gzip "'read' is not defined" NameError.
   Patch by Claudiu Popa.
 
+- Issue #4931: distutils should not produce unhelpful "error: None" messages
+  anymore.  distutils.util.grok_environment_error is kept but doc-deprecated.
+
 - Issue #20283: RE pattern methods now accept the string keyword parameters
   as documented.  The pattern and source keyword parameters are left as
   deprecated aliases.