This guide assumes you have a working install of Trac on Python 2.5/mod_python/Apache2.2 already, as described in the Trac install guide, and that Python 2.6 is installed.

What needs to be done:

• Install Python 2.6 and Trac for 2.6
• Build a new version of mod_python
• Optionally Replace Apache DLLs (mostly if you followed my previous guide)

Required software

You’ll need Visual C++ 2008 Express Edition or any retail version of VS 2008 if you want to build your own mod_python for 2.6 (I’ll provide a precompiled one in this post).

Preparing

Install Python 2.6 and Trac on 2.6 (using “ easy_install trac” is recommended)

You’ll probably also want to easy_install Pygments for source highlighting.

Building mod_python for 2.6

This guide to mod_python covers the creation and installation of a compatible version of the module.

At this point, you should be able to restart Apache and load up your “old” Trac on Python 2.6, but with the error message that “svn” support is not installed.

A pre-built version of this can be found here: mod_python-3.3.2-dev-20080819.win32-py2.6.exe

Python SVN bindings

My old guide had instructions on how to build these yourself, but after that article was made, “official” Python 2.6 bindings have been released.

Most recent version as of this writing is the SVN 1.6.6 version of the bindings.

Replacing Apache DLLs to make libsvn work

Note: Only use these instructions if you experience problems, and/or you’re running a self-built version of the Python SVN bindings already.

There’s a slight difference between libapr-1.dll as supplied with Apache 2.2 and the one we built together with libsvn, so the fix is to replace the one in your Apache2.2\bin folder with the one from your Python2.6\Lib\site-packages\libsvn folder (copy the libsvn_*.dlls from the same folder into the Apache2.2\bin folder if you still get problems).

Restarting Apache now should make Trac work fully, with Subversion support.

So, this how-to will explain the process of building SVN bindings for Python 2.6 on Windows.

What you’ll need:

• Visual C# 2008 Express Edition (Visual Studio 2008 will also work, but will base this on free downloads)
• Swig (I used swigwin-1.3.39 specifically, but any newer version should do)
• Subversion source – grab both the source file subversion-1.6.0.zip and the dependencies subversion-deps-1.6.0.zip

Preparing

Start with installing VC++ 2008 Express and Python if you haven’t already, then create a folder to store the source trees (I used C:\Temp – and will use that folder in the instructions here for simplicity). Unpack Swig to C:\Temp\swig, and subversion-1.6.0.zip and subversion-deps-1.6.0.zip to C:\Temp (which should create the folder “C:\Temp\subversion-1.6.0″).

Make sure you have C:\Python26 in your path.

Creating the Visual Studio solution and compiling

Open a command prompt, go to C:\Temp\subversion-1.6.0, and run the following command:

The paths MUST be absolute like that, using “..\swig” will not work.

This will create the file subversion_vcnet.sln in the folder you’re in – we’ll leave this for a second to build some of the dependencies.

Open the file C:\Temp\subversion-1.6.0\apr\apr.dsw and select “Yes to all” to convert it to VS2008 format, set the build configuration to “Release”, and build.

Do the same thing with C:\Temp\subversion-1.6.0\apr-util\aprutil.dsw (this will ask if you want to use the .vcproj files you already converted in the previous step, answer “Yes” to this) – set to “Release” and build.

Open C:\Temp\subversion-1.6.0\subversion_vcnet.sln in Visual C++ (if you’re using the Express edition, you’ll get a few error messages about project folders not being supported, this won’t affect anything, so just “OK” them), set build configuration to Release (since Python 2.6 by default comes without debug DLLs), and build the sub-project “__SWIG_PYTHON__”.

This should compile with no errors (and few warnings).

Creating the libraries

Now you have all the files you need in C:\Temp\subversion-1.6.0\Release\subversion, so we’ll create the folder C:\Temp\svnpy to hold our “result”.

First, copy the folder C:\Temp\subversion-1.6.0\subversion\bindings\swig\python\svn to C:\Temp\svnpy\svn (this is the pure-python part of the library)

Then, create the folder C:\Temp\svnpy\libsvn and copy C:\Temp\subversion-1.6.0\subversion\bindings\swig\python\*.py here (these are the Swig interface files to the compiled library)

Do a Windows search for “*.dll” in C:\Temp\subversion-1.6.0\Release\subversion (since this will give you a single list of all DLLs in subfolders) and copy all of them to C:\Temp\svnpy\libsvn

Finally, rename all the DLLs starting with underscore (_core, _fs, _delta, _diff, _ra, _wc) from *.dll to *.pyd.

Copy svn and libsvn from C:\Temp\svnpy into C:\Python26\Lib\site-packages to install them.

Testing svn

From a Python command line, try the following:

If this doesn’t throw any errors, you have a working libsvn build!

Troubleshooting

The most common error is getting an exception that says: “_mod” is undefined.

To see the real error, try running the command:

If the error says “DLL load failed: The specified procedure could not be found.”, check if you got all the .dlls copied over from the Release directory – they need to be from your build – even if this is svn 1.6.0, I couldn’t get the “official” 1.6.0 .dlls to work.

If the error is “please reinstall the application”, and there’s an entry in the Windows Event Log to the effect of

“Resolve Partial Assembly failed for Microsoft.VC90.DebugCRT. The referenced assembly is not installed on your system.”

it means one or more of the libsvn*.dlls were compiled in debug mode (even if you set Release when building).

To fix this, open the VC++ 2008 solution again, Ctrl-select all the projects starting with “lib”, Properties, Linker->Debug, and turn off debugging. Re-compile the entire solution, and rebuild the modules as described under “Creating the libraries”