commit b9d4df78db7aaeda1feb58c18b0071934de2361e
Author: Eric89GXL <larson.eric.d@gmail.com>
Date:   Wed Nov 12 10:22:45 2014 -0800

    ENH: Allow not writing home

--- a/mne/utils.py
+++ b/mne/utils.py
@@ -24,6 +24,8 @@ from math import log, ceil
 import json
 import ftplib
 import hashlib
+from functools import partial
+import atexit
 
 import numpy as np
 import scipy
@@ -983,8 +985,12 @@ def get_subjects_dir(subjects_dir=None,
     return subjects_dir
 
 
+_temp_home_dir = None
+
+
 def _get_extra_data_path(home_dir=None):
     """Get path to extra data (config, tables, etc.)"""
+    global _temp_home_dir
     if home_dir is None:
         # this has been checked on OSX64, Linux64, and Win32
         if 'nt' == os.name.lower():
@@ -996,7 +1002,14 @@ def _get_extra_data_path(home_dir=None):
             # of script that isn't launched via the command line (e.g. a script
             # launched via Upstart) then the HOME environment variable will
             # not be set.
-            home_dir = os.path.expanduser('~')
+            if os.getenv('MNE_DONTWRITE_HOME', '') == 'true':
+                if _temp_home_dir is None:
+                    _temp_home_dir = tempfile.mkdtemp()
+                    atexit.register(partial(shutil.rmtree, _temp_home_dir,
+                                            ignore_errors=True))
+                home_dir = _temp_home_dir
+            else:
+                home_dir = os.path.expanduser('~')
 
         if home_dir is None:
             raise ValueError('mne-python config file path could '