Do not use XDG_DATA_HOME. Tell user to use virtualenv if they are not root

lib/util.py

@@ -62,13 +62,15 @@ def data_dir():
     else:
         return appdata_dir()
 
+def usr_share_dir():
+    return os.path.join(sys.prefix, "share")
 
 def appdata_dir():
     """Find the path to the application data directory; add an electrum folder and return path."""
     if platform.system() == "Windows":
         return os.path.join(os.environ["APPDATA"], "Electrum")
     elif platform.system() == "Linux":
-        return os.path.join(sys.prefix, "share", "electrum")
+        return os.path.join(usr_share_dir(), "electrum")
     elif (platform.system() == "Darwin" or
           platform.system() == "DragonFly" or
           platform.system() == "OpenBSD" or

setup.py

@@ -10,14 +10,14 @@ import imp
 
 
 version = imp.load_source('version', 'lib/version.py')
-util = imp.load_source('version', 'lib/util.py')
+util = imp.load_source('util', 'lib/util.py')
 
 if sys.version_info[:3] < (2, 6, 0):
     sys.exit("Error: Electrum requires Python version >= 2.6.0...")
 
-usr_share = '/usr/share'
+usr_share = util.usr_share_dir()
 if not os.access(usr_share, os.W_OK):
-    usr_share = os.getenv("XDG_DATA_HOME", os.path.join(os.getenv("HOME"), ".local", "share"))
+    sys.exit("Error: cannot write to %s.\nIf you do not have root permissions, you may install Electrum a virtualenv.\nAlso, please note that you can run Electrum without installing it on your system."%usr_share)
 
 data_files = []
 if (len(sys.argv) > 1 and (sys.argv[1] == "sdist")) or (platform.system() != 'Windows' and platform.system() != 'Darwin'):
@@ -32,10 +32,7 @@ if (len(sys.argv) > 1 and (sys.argv[1] == "sdist")) or (platform.system() != 'Wi
         if os.path.exists('locale/%s/LC_MESSAGES/electrum.mo' % lang):
             data_files.append((os.path.join(usr_share, 'locale/%s/LC_MESSAGES' % lang), ['locale/%s/LC_MESSAGES/electrum.mo' % lang]))
 
-
+appdata_dir = os.path.join(usr_share, "electrum")
-appdata_dir = util.appdata_dir()
-if not os.access(appdata_dir, os.W_OK):
-    appdata_dir = os.path.join(usr_share, "electrum")
 
 data_files += [
     (appdata_dir, ["data/README"]),