Added normalizing of distribution names in [versions]

The Python package index is case-insensitive. Both
http://pypi.python.org/simple/Django/ and
http://pypi.python.org/simple/dJaNgO/ work. And distributions aren't always
naming themselves consistently case-wise. So all version names are normalized
and case differences won't impact the pinning.

src/zc/buildout/easy_install.py

@@ -171,7 +171,10 @@ class Installer:
         self._index = _get_index(index, links, self._allow_hosts)
 
         if versions is not None:
-            self._versions = versions
+            # Normalize all versions to lowercase. PyPI is case-insensitive
+            # and not all distributions are consistent in their own naming.
+            self._versions = dict([(k.lower(), v)
+                                   for (k, v) in versions.items()])
 
     def _satisfied(self, req, source=None):
         dists = [dist for dist in self._env[req.project_name] if dist in req]
@@ -551,17 +554,9 @@ class Installer:
 
 
     def _constrain(self, requirement):
-        constraint = self._versions.get(requirement.project_name)
-        # REINOUT: use the line below, with the .lower().
-        # Alternative is perhaps to use a self._versions that always uses
-        # lowercase keys.
-        # Actually, this lower-casing happens in buildout-versions, so we need
-        # to do it too. See buildout.py.
-        # constraint = self._versions.get(requirement.project_name.lower())
-
+        constraint = self._versions.get(requirement.project_name.lower())
         if constraint:
             requirement = _constrained_requirement(constraint, requirement)
-
         return requirement
 
     def install(self, specs, working_set=None):
@@ -696,7 +691,8 @@ class Installer:
 def default_versions(versions=None):
     old = Installer._versions
     if versions is not None:
-        Installer._versions = versions
+        Installer._versions = dict([(k.lower(), v)
+                                   for (k, v) in versions.items()])
     return old
 
 def download_cache(path=-1):

src/zc/buildout/repeatable.txt

@@ -280,6 +280,30 @@ When everything is pinned, no output is generated:
     Updating foo.
     recipe v2
 
+The Python package index is case-insensitive. Both
+http://pypi.python.org/simple/Django/ and
+http://pypi.python.org/simple/dJaNgO/ work. And distributions aren't always
+naming themselves consistently case-wise. So all version names are normalized
+and case differences won't impact the pinning:
+
+    >>> write('buildout.cfg',
+    ... '''
+    ... [buildout]
+    ... parts = foo
+    ... find-links = %s
+    ... show-picked-versions = true
+    ...
+    ... [versions]
+    ... distriBUTE = 0.6.34
+    ... Spam = 2
+    ...
+    ... [foo]
+    ... recipe = spam
+    ... ''' % join('recipe', 'dist'))
+    >>> print_(system(buildout), end='') # doctest: +ELLIPSIS
+    Updating foo.
+    recipe v2
+
 
 Controlling the python version
 -------------------------------