If a package has directories with names in APP CAPS, distutils.commands.bdist_msi creates properties for them that are also in all caps.

Such properties are handled specially by MSI and are called "public properties (http://www.advancedinstaller.com/user-guide/properties.html).

Due to the way bdist_msi-produced .msi's work, this ultimately results in subtrees of these directories being duplicated to a bogus location (the root directory of the drive on which the .msi being installed is).

E.g. in the attached example, all <python>\Lib\mercurial\locale\<code>\LC_MESSAGES subtrees got duplicated to D:\Lib\<etc>.

See https://bz.mercurial-scm.org/show_bug.cgi?id=5192 for details (including a high-level description of how bdist_msi packages work).