Merged revisions 61602-61723 via svnmerge from
svn+ssh://pythondev@svn.python.org/sandbox/trunk/2to3/lib2to3

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  r61626 | david.wolever | 2008-03-19 17:19:16 +0100 (Mi, 19 Mär 2008) | 1 line

  Added fixer for implicit local imports.  See #2414.
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  r61628 | david.wolever | 2008-03-19 17:57:43 +0100 (Mi, 19 Mär 2008) | 1 line

  Added a class for tests which should not run if a particular import is found.
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  r61629 | collin.winter | 2008-03-19 17:58:19 +0100 (Mi, 19 Mär 2008) | 1 line

  Two more relative import fixes in pgen2.
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  r61635 | david.wolever | 2008-03-19 20:16:03 +0100 (Mi, 19 Mär 2008) | 1 line

  Fixed print fixer so it will do the Right Thing when it encounters __future__.print_function.  2to3 gets upset, though, so the tests have been commented out.
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  r61637 | david.wolever | 2008-03-19 21:37:17 +0100 (Mi, 19 Mär 2008) | 3 lines

  Added a fixer for itertools imports (from itertools import imap, ifilterfalse --> from itertools import filterfalse)
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  r61645 | david.wolever | 2008-03-19 23:22:35 +0100 (Mi, 19 Mär 2008) | 1 line

  SVN is happier when you add the files you create... -_-'
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  r61654 | david.wolever | 2008-03-20 01:09:56 +0100 (Do, 20 Mär 2008) | 1 line

  Added an explicit sort order to fixers -- fixes problems like #2427
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  r61664 | david.wolever | 2008-03-20 04:32:40 +0100 (Do, 20 Mär 2008) | 3 lines

  Fixes #2428 -- comments are no longer eatten by __future__ fixer.
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  r61673 | david.wolever | 2008-03-20 17:22:40 +0100 (Do, 20 Mär 2008) | 1 line

  Added 2to3 node pretty-printer
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  r61679 | david.wolever | 2008-03-20 20:50:42 +0100 (Do, 20 Mär 2008) | 1 line

  Made node printing a little bit prettier
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  r61723 | martin.v.loewis | 2008-03-22 00:59:27 +0100 (Sa, 22 Mär 2008) | 2 lines

  Fix whitespace.
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diff --git a/Lib/lib2to3/fixes/basefix.py b/Lib/lib2to3/fixes/basefix.py
index 66c448e..87fa205 100644
--- a/Lib/lib2to3/fixes/basefix.py
+++ b/Lib/lib2to3/fixes/basefix.py
@@ -16,6 +16,7 @@
 # Local imports
 from ..patcomp import PatternCompiler
 from .. import pygram
+from .util import does_tree_import
 
 class BaseFix(object):
 
@@ -36,6 +37,8 @@
     used_names = set() # A set of all used NAMEs
     order = "post" # Does the fixer prefer pre- or post-order traversal
     explicit = False # Is this ignored by refactor.py -f all?
+    run_order = 5   # Fixers will be sorted by run order before execution
+                    # Lower numbers will be run first.
 
     # Shortcut for access to Python grammar symbols
     syms = pygram.python_symbols
@@ -163,3 +166,23 @@
         filename - the name of the file the tree came from.
         """
         pass
+
+
+class ConditionalFix(BaseFix):
+    """ Base class for fixers which not execute if an import is found. """
+
+    # This is the name of the import which, if found, will cause the test to be skipped
+    skip_on = None
+
+    def start_tree(self, *args):
+        super(ConditionalFix, self).start_tree(*args)
+        self._should_skip = None
+
+    def should_skip(self, node):
+        if self._should_skip is not None:
+            return self._should_skip
+        pkg = self.skip_on.split(".")
+        name = pkg[-1]
+        pkg = ".".join(pkg[:-1])
+        self._should_skip = does_tree_import(pkg, name, node)
+        return self._should_skip