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

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

Doc/distutils/apiref.rst

@@ -1167,15 +1167,6 @@ 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:`EnvironmentError`  (:exc:`IOError`
-   or :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)
 

Lib/distutils/core.py

@@ -14,7 +14,6 @@ import os
 from distutils.debug import DEBUG
 from distutils.errors import (DistutilsSetupError, DistutilsArgError,
                               DistutilsError, CCompilerError)
-from distutils.util import grok_environment_error
 
 # Mainly import these so setup scripts can "from distutils.core import" them.
 from distutils.dist import Distribution
@@ -153,13 +152,11 @@ def setup(**attrs):
         except KeyboardInterrupt:
             raise SystemExit, "interrupted"
         except (IOError, os.error), 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, exc
 
         except (DistutilsError,
                 CCompilerError), msg:

Lib/distutils/dir_util.py

@@ -185,7 +185,6 @@ 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:
@@ -202,8 +201,7 @@ def remove_tree(directory, verbose=1, dry_run=0):
             if abspath in _path_created:
                 del _path_created[abspath]
         except (IOError, OSError), 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

@@ -3,8 +3,9 @@ import sys
 import unittest
 from test.test_support import run_unittest
 
-from distutils.errors import DistutilsPlatformError, DistutilsByteCompileError
-from distutils.util import byte_compile
+from distutils.errors import DistutilsByteCompileError
+from distutils.util import byte_compile, grok_environment_error
+
 
 class UtilTestCase(unittest.TestCase):
 
@@ -18,6 +19,13 @@ class UtilTestCase(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[-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

@@ -44,6 +44,9 @@ Library
   as documented.  The pattern and source keyword parameters are left as
   deprecated aliases.
 
+- Issue #4931: distutils should not produce unhelpful "error: None" messages
+  anymore.  distutils.util.grok_environment_error is kept but doc-deprecated.
+
 - Improve the random module's default seeding to use 256 bits of entropy
   from os.urandom().  This was already done for Python 3, mildly improving
   security with a bigger seed space.