fix: setup.py change again. Make data files relative.

Keep make_data_files_absolute(data_files, prefix), but make it a no-op
via parameter in case it needs to be reverted in the field.

When run under pip, the data files are re-parented to the prefix
directory even when they are absolute. So I get paths like:

  /usr/local/venv/usr/local/venv/share/{roundup,man,docs,locale,...}/...

rather than:

  /usr/local/venv/share/{roundup,man,docs,locale,...}/...

Roundup is finding them in either place, but /usr/local/venv/share is
easier for humans who need to be able to find man pages, html docs,
example code, frontend integration code (wsgi, cgi, zope) to modify.

Running 'roundup-admin templates' can give the user a hint where the
share directory is.

I feel like I keep going around and around on this. I have decided to
make pip install in a venv the standard path for installation. So make
the code work for that path and if it breaks all the other ways to
install, well that's the realm of Python packaging.

The internal code that searches a bunch of places to try to find its
files is not changed.

Author: rouilj

setup.py

@@ -52,7 +52,7 @@ def mapscript(path):
     return '%s = roundup.scripts.%s:run' % (script, module)
 
 
-def make_data_files_absolute(data_files, prefix):
+def make_data_files_absolute(data_files, prefix, enable=False):
     """Using setuptools data files are put under the egg install directory
        if the datafiles are relative paths. We don't want this. Data files
        like man pages, documentation, templates etc. should be installed
@@ -63,8 +63,9 @@ def make_data_files_absolute(data_files, prefix):
     """
     new_data_files = [ (os.path.join(prefix,df[0]),df[1])
                        for df in data_files ]
-
-    return new_data_files
+    if enable:
+        return new_data_files
+    return data_files
 
 
 def get_prefix():