s4-python: Install external packages to a different directory but import into

the normal namespace when the system doesn't have it available.

source4/script/installmisc.sh

@@ -83,12 +83,13 @@ cp setup/provision.smb.conf.standalone $SETUPDIR || exit 1
 
 echo "Installing external python libraries"
 mkdir -p $DESTDIR$PYTHONDIR || exit 1
-for p in $($PYTHON scripting/python/samba_external/missing.py);
+MISSING="$($PYTHON scripting/python/samba_external/missing.py)"
+for p in $MISSING
 do
   package=`basename $p`
   echo "Installing missing python package $package"
-  mkdir -p $DESTDIR$PYTHONDIR/$package
-  cp -r ../lib/$p/* $DESTDIR$PYTHONDIR/$package/ || exit 1
+  mkdir -p $DESTDIR$PYTHONDIR/samba/external/$package
+  cp -r ../lib/$p/* $DESTDIR$PYTHONDIR/samba/external/$package/ || exit 1
 done
 
 echo "Installing stuff in $PRIVATEDIR"

source4/scripting/bin/samba_dnsupdate

@@ -38,7 +38,7 @@ from samba import glue
 from samba.auth import system_session
 from samba.samdb import SamDB
 
-samba.ensure_external_module("dns.resolver", "dnspython")
+samba.ensure_external_module("dns", "dnspython")
 import dns.resolver as resolver
 
 default_ttl = 900

source4/scripting/python/samba/__init__.py

@@ -402,10 +402,15 @@ def ensure_external_module(modulename, location):
     try:
         __import__(modulename)
     except ImportError:
-        sys.path.insert(0, 
-            os.path.join(os.path.dirname(__file__),
-                         "../../../../lib", location))
-        __import__(modulename)
+        import sys
+        if _in_source_tree():
+            sys.path.insert(0, 
+                os.path.join(os.path.dirname(__file__),
+                             "../../../../lib", location))
+            __import__(modulename)
+        else:
+            sys.modules[modulename] = __import__(
+                "samba.external.%s" % modulename, fromlist=["samba.external"])
 
 version = glue.version