Avoid environment variables with a dot in them

git-svn-id: http://svn.zope.org/repos/main/zc.buildout/trunk@120916 62d5b8a3-27da-0310-9561-8e5933582275

DEVELOPERS.txt

@@ -12,10 +12,14 @@ When you're developing buildout itself, you need to know two things:
 
 +1 for testing:
 
-- You should have specific python versions at specific locations or
-  PYTHONx.x environment variables pointing to those
+- You should have specific python executable versions at specific locations or
+  PYTHONxy environment variables pointing to those
   See zc.buildout testing.py, def find_python(version)
 
-  The way to start the tests for Python 2.5 for instance would be::
+  If you use python2.5 to test then the test runner will look for
+  python2.6 in your path. If you use any other python version it will look for
+  python2.5 in your path or it will look for the PYTHON25 environment variable.
+  
+  To start the tests with Python 2.7 for instance would be::
 
-    $ env PYTHON2.5=/path/to/python2.5 bin/test
+    $ env PYTHON25=/path/to/bin/python2.5 bin/test

src/zc/buildout/testing.py

@@ -160,11 +160,13 @@ def sys_install(setup, dest):
               '--single-version-externally-managed')
 
 def find_python(version):
-    e = os.environ.get('PYTHON%s' % version)
+    env_friendly_version = ''.join(version.split('.'))
+    
+    e = os.environ.get('PYTHON%s' % env_friendly_version)
     if e is not None:
         return e
     if is_win32:
-        e = '\Python%s%s\python.exe' % tuple(version.split('.'))
+        e = '\Python%s\python.exe' % env_friendly_version
         if os.path.exists(e):
             return e
     else: