Merge pull request RIPE-NCC#126 from danielquinn/docs/installation-tr…

…ouble

A few documentation additions

docs/installation.rst

@@ -36,11 +36,11 @@ Debian/Ubuntu
 
 The following has been tested on Debian Jessie.
 
-Debian-based distributions require two system packages to be installed first:
+Debian-based distributions require three system packages to be installed first:
 
 .. code:: bash
 
-    sudo apt-get install python-dev libffi-dev
+    sudo apt-get install python-dev libffi-dev libssl-dev
 
 You'll also need either ``virtualenv`` (recommended), or if you're not
 comfortable with that, at the very least, you'll need ``pip``:

docs/troubleshooting.rst

@@ -37,3 +37,29 @@ their machines.  Workarounds and proper fixes for this issue can be found in the
 `Sagan installation documentation`_.
 
 .. _Sagan installation documentation: https://ripe-atlas-sagan.readthedocs.org/en/latest/installation.html#troubleshooting
+
+Complaints from libyaml
+-----------------------
+
+During the installation, you may see something like this scroll by:
+
+    Running setup.py install for pyyaml
+      checking if libyaml is compilable
+      x86_64-linux-gnu-gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.7 -c build/temp.linux-x86_64-2.7/check_libyaml.c -o build/temp.linux-x86_64-2.7/check_libyaml.o
+      build/temp.linux-x86_64-2.7/check_libyaml.c:2:18: fatal error: yaml.h: No such file or directory
+       #include <yaml.h>
+                      ^
+      compilation terminated.
+
+      libyaml is not found or a compiler error: forcing --without-libyaml
+      (if libyaml is installed correctly, you may need to
+       specify the option --include-dirs or uncomment and
+       modify the parameter include_dirs in setup.cfg)
+
+Don't worry.  This is just the installation script noticing that you don't have
+libyaml installed and it's complaining because it's good to have around for
+performance reasons.  However, since we're only using YAML for configuration,
+performance isn't an issue, and the fallback option will be sufficient.
+
+If however, you don't like these sorts of errors, make sure that libyaml is
+installed for your distribution before attempting to install this toolkit.