core: apply wokkel patches if they are not already:

this case may happen if a sat module is used without the backend being launched (e.g. in
tests)

sat/__init__.py

@@ -1,6 +1,5 @@
 #!/usr/bin/env python3
 
-
 # Libervia: an XMPP client
 # Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
 
@@ -17,11 +16,12 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 import os.path
+from sat_tmp import wokkel
 
 version_file = os.path.join(os.path.dirname(__file__), "VERSION")
-try:
-    with open(version_file) as f:
-        __version__ = f.read().strip()
-except NotImplementedError:
-    # pyjamas workaround
-    __version__ = "0.7.0D"
+with open(version_file) as f:
+    __version__ = f.read().strip()
+
+if not wokkel.installed:
+    print("installing Wokkel patches")
+    wokkel.install()