s4-python: allow us to have samba copies of python libraries we depend on

For python libraries like dns.resolver it is useful to be able to install 
a copy of the library with Samba. This set of functions allows us to do that
while using the locally installed version if it is available

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

1 files changed, 50 insertions, 0 deletions

diff --git a/source4/scripting/python/samba/external.py b/source4/scripting/python/samba/external.py
new file mode 100644
index 0000000000..eca910b794
--- /dev/null
+++ b/source4/scripting/python/samba/external.py
@@ -0,0 +1,50 @@
+#!/usr/bin/python
+
+# Unix SMB/CIFS implementation.
+# Copyright (C) Andrew Tridgell 2010
+#
+# 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 sys, os
+
+def samba_find_external(directory):
+    '''insert into out module search path the path to an
+       external library'''
+    for p in sys.path:
+        dir = os.path.join(p, directory)
+        if os.path.isdir(dir):
+            sys.path.insert(0, dir)
+            return
+
+    # finally try in the local directory, to handle in-tree testing
+    dir = os.path.join("scripting/python", directory)
+    if os.path.isdir(dir):
+        sys.path.insert(0, dir)
+        return
+
+    print "Failed to find external python library %s" % directory
+    raise
+
+
+def samba_external_dns_resolver():
+    '''try and import the dns.resolver library, and if it fails
+    then use a local copy from the external directory'''
+
+    try:
+        import dns.resolver as dns
+    except:
+        samba_find_external("samba_external/dnspython")
+        import dns.resolver as dns
+    return dns