add #125 and #129 to troubleshooting

docs/docs/install.rst

@@ -10,6 +10,8 @@ next section carefully.
     :local:
     :depth: 1
 
+ .. _install-interludium:
+
 Interludium: Python is not PHP
 ------------------------------
 

docs/docs/troubleshooting.rst

@@ -1,4 +1,18 @@
 Troubleshooting
 ===============
 
-To be written.
+pkg_ressources.DistributionNotFound
+-----------------------------------
+
+This is usually caused by messing up the system's Python with newer packages
+from PyPi (e.g. by executing `easy_install --upgrade pip` as root) and is not
+related to Isso at all.
+
+Install Isso in a virtual environment as described in
+:ref:`install-interludium`. Alternatively, you can use `pip install --user`
+to install Isso into the user's home.
+
+The web console shows 404 Not Found responses
+---------------------------------------------
+
+That's fine. Isso returns "404 Not Found" to indicate "No comments".