Fix bug 1216: Remove machines only for native charms

Updates revision of Python libjuju to 2.8.4

Change-Id: I3f41eead305349eba5d404f5f3d61d33f0536aca
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/setup.py b/setup.py
index 0c874f1..b102779 100644
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,7 @@
     packages=find_packages(
         exclude=["*.tests", "*.tests.*", "tests.*", "tests"]),
     install_requires=[
-        'juju==2.8.2',
+        'juju==2.8.4',
         'paramiko',
         'pyasn1>=0.4.4',
         'kubernetes==10.0.1'