Fix Python3 compatibility in _android.pyx

Author: darosior

pythonforandroid/recipes/android/src/android/_android.pyx

@@ -174,8 +174,10 @@ from jnius import autoclass, PythonJavaClass, java_method, cast
 api_version = autoclass('android.os.Build$VERSION').SDK_INT
 version_codes = autoclass('android.os.Build$VERSION_CODES')
 
-
-python_act = autoclass(JAVA_NAMESPACE.decode('utf8') + u'.PythonActivity')
+import sys
+if sys.version_info[0] == 2:
+    JAVA_NAMESPACE = JAVA_NAMESPACE.decode('utf-8')
+python_act = autoclass(JAVA_NAMESPACE + u'.PythonActivity')
 Rect = autoclass(u'android.graphics.Rect')
 mActivity = python_act.mActivity
 if mActivity: