Use a temporary directory as egg cache

We have use with broken permission on their
system. We try to workaround the issue.

Fix #182

gns3server/main.py

@@ -16,6 +16,16 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+
+# WARNING
+# Due to buggy user machines we choose to put this as the first loading modules
+# otherwise the egg cache is initialized in his standard location and
+# if is not writetable the application crash. It's the user fault
+# because one day the user as used sudo to run an egg and break his
+# filesystem permissions, but it's a common mistake.
+import gns3server.utils.get_resource
+
+
 import os
 import datetime
 import sys

gns3server/utils/get_resource.py

@@ -0,0 +1,41 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2015 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import tempfile
+import pkg_resources
+import atexit
+import logging
+
+log = logging.getLogger(__name__)
+
+try:
+    egg_cache_dir = tempfile.mkdtemp()
+    pkg_resources.set_extraction_path(dir)
+except ValueError:
+    # If the path is already set the module throw an error
+    pass
+
+
+@atexit.register
+def clean_egg_cache():
+    try:
+        import shutil
+        log.debug("Clean egg cache %s", egg_cache_dir)
+        shutil.rmtree(egg_cache_dir)
+    except Exception:
+        # We don't care if we can not cleanup
+        pass