docs: add information about extra dependencies we now need

We have always needed some development packages, but never said
that explicitly. Now that bcrypt also requires libffi-dev, we
should mention that.

docs/installation.rst

@@ -1,124 +1,140 b''
 .. _installation:
 
 ==========================
 Installation on Unix/Linux
 ==========================
 
 The following describes three different ways of installing Kallithea:
 
 - :ref:`installation-source`: The simplest way to keep the installation
   up-to-date and track any local customizations is to run directly from
   source in a Kallithea repository clone, preferably inside a virtualenv
   virtual Python environment.
 
 - :ref:`installation-virtualenv`: If you prefer to only use released versions
   of Kallithea, the recommended method is to install Kallithea in a virtual
   Python environment using `virtualenv`. The advantages of this method over
   direct installation is that Kallithea and its dependencies are completely
   contained inside the virtualenv (which also means you can have multiple
   installations side by side or remove it entirely by just removing the
   virtualenv directory) and does not require root privileges.
 
 - :ref:`installation-without-virtualenv`: The alternative method of installing
   a Kallithea release is using standard pip. The package will be installed in
   the same location as all other Python packages you have ever installed. As a
   result, removing it is not as straightforward as with a virtualenv, as you'd
   have to remove its dependencies manually and make sure that they are not
   needed by other packages.
 
+Regardless of the installation method you may need to make sure you have
+appropriate development packages installed, as installation of some of the
+Kallithea dependencies requires a working C compiler and libffi library
+headers. Depending on your configuration, you may also need to install
+Git and development packages for the database of your choice.
+
+For Debian and Ubuntu, the following command will ensure that a reasonable
+set of dependencies is installed::
+
+    sudo apt-get install build-essential git python-pip python-virtualenv libffi-dev python-dev
+
+For Fedora and RHEL-derivatives, the following command will ensure that a
+reasonable set of dependencies is installed::
+
+    sudo yum install gcc git python-pip python-virtualenv libffi-devel python-devel
+
 .. _installation-source:
 
 
 Installation from repository source
 -----------------------------------
 
 To install Kallithea in a virtualenv_ using the stable branch of the development
 repository, follow the instructions below::
 
         hg clone https://kallithea-scm.org/repos/kallithea -u stable
         cd kallithea
         virtualenv ../kallithea-venv
         source ../kallithea-venv/bin/activate
         pip install --upgrade pip setuptools
         pip install -e .
         python2 setup.py compile_catalog   # for translation of the UI
 
 You can now proceed to :ref:`setup`.
 
 .. _installation-virtualenv:
 
 
 Installing a released version in a virtualenv
 ---------------------------------------------
 
 It is highly recommended to use a separate virtualenv_ for installing Kallithea.
 This way, all libraries required by Kallithea will be installed separately from your
 main Python installation and other applications and things will be less
 problematic when upgrading the system or Kallithea.
 An additional benefit of virtualenv_ is that it doesn't require root privileges.
 
 - Assuming you have installed virtualenv_, create a new virtual environment
   for example, in `/srv/kallithea/venv`, using the virtualenv command::
 
     virtualenv /srv/kallithea/venv
 
 - Activate the virtualenv_ in your current shell session and make sure the
   basic requirements are up-to-date by running::
 
     source /srv/kallithea/venv/bin/activate
     pip install --upgrade pip setuptools
 
 .. note:: You can't use UNIX ``sudo`` to source the ``virtualenv`` script; it
    will "activate" a shell that terminates immediately. It is also perfectly
    acceptable (and desirable) to create a virtualenv as a normal user.
 
 .. note:: Some dependencies are optional. If you need them, install them in
    the virtualenv too::
 
      pip install psycopg2
      pip install python-ldap
 
    This might require installation of development packages using your
    distribution's package manager.
 
 - Make a folder for Kallithea data files, and configuration somewhere on the
   filesystem. For example::
 
     mkdir /srv/kallithea
 
 - Go into the created directory and run this command to install Kallithea::
 
     pip install kallithea
 
   Alternatively, download a .tar.gz from http://pypi.python.org/pypi/Kallithea,
   extract it and run::
 
     pip install .
 
 - This will install Kallithea together with pylons_ and all other required
   python libraries into the activated virtualenv.
 
 You can now proceed to :ref:`setup`.
 
 .. _installation-without-virtualenv:
 
 
 Installing a released version without virtualenv
 ------------------------------------------------
 
 For installation without virtualenv, 'just' use::
 
     pip install kallithea
 
 Note that this method requires root privileges and will install packages
 globally without using the system's package manager.
 
 To install as a regular user in ``~/.local``, you can use::
 
     pip install --user kallithea
 
 You can now proceed to :ref:`setup`.
 
 
 .. _virtualenv: http://pypi.python.org/pypi/virtualenv
 .. _pylons: http://www.pylonsproject.org/