Merge pull request #135 from branfosj/requirements

only list requirements once on installation page

docs/installation.md

@@ -16,18 +16,22 @@ Notes on other ways of installing EasyBuild are available under section [Alterna
 
 The only strict requirements are:
 
-* a **GNU/Linux distribution** as operating system
-* **Python**:
-    * Python 2.7, or Python 3.x (>= 3.5). Since [Python 2 is end-of-life](https://www.python.org/doc/sunset-python-2/) we recommend
-      using Python 3 if it is available
-    * **note**: only EasyBuild v4.0 (or newer) is compatible with Python 3, earlier EasyBuild releases require Python 2
-    * no Python packages other than the ones included in the Python standard library are strictly required
-    * for some specific features, additional Python packages are needed though, see [Optional Python packages][optional_python_packages]
+* a **GNU/Linux** distribution as operating system
+    * some common shell tools are expected to be available, see [Required shell tools][required_shell_tools]
+* [Python](https://python.org):
+    * Python 2.7, or Python 3.x (>= 3.5);
+    * since [Python 2 is end-of-life](https://www.python.org/doc/sunset-python-2/) we strongly recommend
+      using Python 3 if it is available;
+    * only EasyBuild v4.0 (or newer) is compatible with Python 3, earlier EasyBuild releases require Python 2;
+    * EasyBuild 5.0 will require Python >= 3.6;
+    * no third-party Python packages are strictly required (the Python standard library is sufficient);
+    * for some *specific* EasyBuild features additional Python packages are required however, see [Optional Python packages][optional_python_packages];
 * a **modules tool**: Tcl(/C) environment modules or Lmod
-    * the actual module command/script (`modulecmd`, `modulecmd.tcl` or `lmod`) *must* be available via `$PATH`
-    * see [Required modules tool][required_modules_tool] for more details
+    * the actual modules tool *must* be available via `$PATH`, see [Required modules tool][required_modules_tool]
+* a C/C++ compiler (e.g., `gcc` and `g++`)
+    * only required to build and install GCC with, or as a dependency for the Intel compilers, for example
 
-For more information on (optional) dependencies, see [Dependencies][dependencies].
+For more information on dependencies, see [Dependencies][dependencies].
 
 
 ## Using pip to Install EasyBuild {: #pip }
@@ -303,28 +307,12 @@ module load EasyBuild
     The environment module file that was generated by EasyBuild specifies all changes that need to be made.
 
 
-## Dependencies {: #dependencies }
+## Required Dependencies {: #dependencies }
 
-EasyBuild has a couple of dependencies, some are optional.
+This section gives further information on the [required dependencies][requirements].
 
 
-### Required dependencies {: #required_dependencies }
-
-* a **GNU/Linux** distribution as operating system
-    * some common shell tools are expected to be available, see [Required shell tools][required_shell_tools]
-* [Python](https://python.org):
-    * Python 2.7, or Python 3.x (>= 3.5);
-    * since [Python 2 is end-of-life](https://www.python.org/doc/sunset-python-2/) we strongly recommend
-      using Python 3 if it is available;
-    * no third-party Python packages are strictly required (the Python standard library is sufficient);
-    * for some *specific* EasyBuild features additional Python packages are required however, see [Optional Python packages][optional_python_packages];
-* a **modules tool**: Tcl(/C) environment modules or Lmod
-    * the actual modules tool *must* be available via `$PATH`, see [Required modules tool][required_modules_tool]
-* a C/C++ compiler (e.g., `gcc` and `g++`)
-    * only required to build and install GCC with, or as a dependency for the Intel compilers, for example
-
-
-#### Required shell tools {: #required_shell_tools }
+### Required shell tools {: #required_shell_tools }
 
 <!-- XXX - UPDATE BY VERSION, below -->
 
@@ -342,7 +330,7 @@ A couple of shell tools may be required, depending on the particular use case (i
 * `sysctl`, for querying system characteristics (only required on non-Linux systems)
 
 
-#### Required modules tool {: #required_modules_tool }
+### Required modules tool {: #required_modules_tool }
 
 EasyBuild not only generates module files to be used along with the software it installs,
 it also depends on the generated modules, mainly for resolving dependencies.
@@ -388,17 +376,16 @@ Additional notes:
   [Installing Lmod without root permissions][installing_lmod].
 
 
-#### Required Python packages {: #required_python_packages }
+### Required Python packages {: #required_python_packages }
 
 Since EasyBuild v4.0, *no* Python packages outside of the Python standard library are required.
 
-
-### Optional dependencies
+## Optional dependencies
 
 Some dependencies are optional and are only required to support certain features.
 
 
-#### Optional Python packages {: #optional_python_packages }
+### Optional Python packages {: #optional_python_packages }
 
 * [GC3Pie](https://pypi.org/project/gc3pie), only needed when using `GC3Pie` as a backend for `--job`,
   see also [Submitting jobs using --job][submitting_jobs];