A few different ways to delete all .svn files from a git repository's history.

remove_svn.py

#!/bin/python

# USAGE: 
# 1) cd /path/to/git/repository
# 2) execute the script with:  `python /path/to/remove_svn.py`
# NOTE: By default this code does a dry-run. To actually delete files from history, remove the
# "n" flag from the 'git rm -rfn' around line 20.

import subprocess
p = subprocess.Popen(['find', '.', '-name', '*.svn'], stdout=subprocess.PIPE)
svnlist, err = p.communicate()

files = ''

for filepath in svnlist.split('\n'):
    if filepath and filepath != '\n':
        q = subprocess.Popen(['git', 'filter-branch',  '-f', '--index-filter',
            str('git rm -rfn --cached --ignore-unmatch ' + filepath),
            '--prune-empty'],
            stdout=subprocess.PIPE)
        out, err = q.communicate()
        print out

remove_svn.sh

# Usage:
# 1) cd /path/to/git/repository
# 2) paste this code and run.

# NOTE: By default this does a dry-run. Remove the "n" flag from the 'git rm -rfn' near the
# the end of the line to really delete history.

find . -name '*.svn' | xargs -I {} git filter-branch -f --prune-empty --index-filter "git rm -rfn --cached --ignore-unmatch {}"