Revert "Updated to work with the latest setuptools." partially

One big issue in commit e129e187 is that the
initial value of buildout_and_setuptools_path can cause buildout to use a lot
of CPU at startup. The following change would help:

    def buildout_and_setuptools_path():
        r = [get_python_lib(standard_lib=1)]
        for d in pkg_resources.working_set:
            d = d.location
            if d not in r:
                r.append(d)
        return r[1:]
    buildout_and_setuptools_path = buildout_and_setuptools_path()

but initializing buildout_and_setuptools_dists also takes time to compute,
and it's only used for bootstrap.

Because the commit is not required anymore since setuptools 36, it's easier
for us to revert partially, so we can keep applying our patches.

src/zc/buildout/buildout.py

@@ -439,10 +439,12 @@ class Buildout(DictMixin):
 
         # Now copy buildout and setuptools eggs, and record destination eggs:
         entries = []
-        for dist in zc.buildout.easy_install.buildout_and_setuptools_dists:
+        for name in 'zc.buildout', 'setuptools':
+            r = pkg_resources.Requirement.parse(name)
+            dist = pkg_resources.working_set.find(r)
             if dist.precedence == pkg_resources.DEVELOP_DIST:
                 dest = os.path.join(self['buildout']['develop-eggs-directory'],
-                                    dist.key + '.egg-link')
+                                    name+'.egg-link')
                 open(dest, 'w').write(dist.location)
                 entries.append(dist.location)
             else:
@@ -1093,6 +1095,7 @@ class Buildout(DictMixin):
         fd, tsetup = tempfile.mkstemp()
         try:
             os.write(fd, (zc.buildout.easy_install.runsetup_template % dict(
+                setuptools=zc.buildout.easy_install.setuptools_pythonpath,
                 setupdir=os.path.dirname(setup),
                 setup=setup,
                 __file__ = setup,

src/zc/buildout/easy_install.py

@@ -74,11 +74,16 @@ if has_distribute and not has_setuptools:
              " you have the latest version downloaded from"
              " https://bootstrap.pypa.io/bootstrap-buildout.py")
 
-# Include buildout and setuptools eggs in paths.  We get this
-# initially from the entire working set.  Later, we'll use the install
-# function to narrow to just the buildout and setuptools paths.
-buildout_and_setuptools_path = [d.location for d in pkg_resources.working_set]
-setuptools_path = buildout_and_setuptools_path
+setuptools_pythonpath = pkg_resources.working_set.find(
+    pkg_resources.Requirement.parse('setuptools')
+    ).location
+
+# Include buildout and setuptools eggs in paths
+buildout_and_setuptools_path = [
+    pkg_resources.working_set.find(
+        pkg_resources.Requirement.parse('zc.buildout')).location,
+    setuptools_pythonpath,
+    ]
 
 FILE_SCHEME = re.compile('file://', re.I).match
 DUNDER_FILE_PATTERN = re.compile(r"__file__ = '(?P<filename>.+)'$")
@@ -336,10 +341,10 @@ class Installer:
 
         tmp = tempfile.mkdtemp(dir=dest)
         try:
-            path = setuptools_path
+            path = setuptools_pythonpath
 
             args = [sys.executable, '-c',
-                    ('import sys; sys.path[0:0] = %r; ' % path) +
+                    ('import sys; sys.path[0:0] = [%r]; ' % path) +
                     _easy_install_cmd, '-mZUNxd', tmp]
             level = logger.getEffectiveLevel()
             if level > 0:
@@ -892,13 +897,6 @@ def install(specs, dest,
                           check_picked=check_picked)
     return installer.install(specs, working_set)
 
-buildout_and_setuptools_dists = list(install(['zc.buildout'], None,
-                                             check_picked=False))
-buildout_and_setuptools_path = [d.location
-                                for d in buildout_and_setuptools_dists]
-setuptools_path = [d.location
-                   for d in install(['setuptools'], None, check_picked=False)]
-setuptools_pythonpath = os.pathsep.join(setuptools_path)
 
 def build(spec, dest, build_ext,
           links=(), index=None,
@@ -1014,6 +1012,7 @@ def develop(setup, dest,
         undo.append(lambda: os.close(fd))
 
         os.write(fd, (runsetup_template % dict(
+            setuptools=setuptools_pythonpath,
             setupdir=directory,
             setup=setup,
             __file__ = setup,
@@ -1437,19 +1436,18 @@ if _interactive:
 
 runsetup_template = """
 import sys
-sys.path.insert(0, %%(setupdir)r)
-sys.path[0:0] = %r
+sys.path[:0] = %(setuptools)r, %(setupdir)r
 
 import os, setuptools
 
-__file__ = %%(__file__)r
+__file__ = %(__file__)r
 
-os.chdir(%%(setupdir)r)
-sys.argv[0] = %%(setup)r
+os.chdir(%(setupdir)r)
+sys.argv[0] = %(setup)r
 
-with open(%%(setup)r, 'U') as f:
-    exec(compile(f.read(), %%(setup)r, 'exec'))
-""" % setuptools_path
+with open(%(setup)r, 'U') as f:
+    exec(compile(f.read(), %(setup)r, 'exec'))
+"""
 
 
 class VersionConflict(zc.buildout.UserError):

src/zc/buildout/tests.py

@@ -34,6 +34,14 @@ os_path_sep = os.path.sep
 if os_path_sep == '\\':
     os_path_sep *= 2
 
+def buildout_and_setuptools_dists():
+    # lazy or the index cache would be filled using wrong default_index_url
+    global buildout_and_setuptools_dists
+    x = list(zc.buildout.easy_install.install(
+        ['zc.buildout'], None, check_picked=False))
+    buildout_and_setuptools_dists = lambda: x
+    return x
+
 
 def develop_w_non_setuptools_setup_scripts():
     """
@@ -2501,7 +2509,7 @@ honoring our version specification.
     ... eggs = foo
     ... ''' % ('\n'.join(
     ...     '%s = %s' % (d.key, d.version)
-    ...     for d in zc.buildout.easy_install.buildout_and_setuptools_dists)))
+    ...     for d in buildout_and_setuptools_dists())))
 
     >>> print_(system(buildout), end='')
     Installing foo.
@@ -3363,7 +3371,7 @@ def updateSetup(test):
     test.globs['new_releases'] = new_releases
     ws = getWorkingSetWithBuildoutEgg(test)
     # now let's make the new releases
-    for dist in zc.buildout.easy_install.buildout_and_setuptools_dists:
+    for dist in buildout_and_setuptools_dists():
         makeNewRelease(dist.key, ws, new_releases)
         os.mkdir(os.path.join(new_releases, dist.key))