Add the rockstar package (#3680)

* Add the rockstar package

* Add rockstar to yt.

* Correct signature of prep_yt.

* Correct rockstar package installation process

Needed to change the way the necessary prefixes are found as well as
how the completed package is copied.

There should probably be a way to do the copying in a more 'spack' way.

* Add license

* Add description.

* Set no hdf5 variant as default.

* Use copy_tree for copying files

* Use MakefilePackage

* Address concerns from @adamjstewart

* Fix flake8 errors.

var/spack/repos/builtin/packages/py-yt/package.py

@@ -57,6 +57,7 @@ class PyYt(PythonPackage):
     variant("astropy", default=True, description="enable astropy support")
     variant("h5py", default=True, description="enable h5py support")
     variant("scipy", default=True, description="enable scipy support")
+    variant("rockstar", default=False, description="enable rockstar support")
 
     depends_on("py-astropy", type=('build', 'run'), when="+astropy")
     depends_on("py-cython", type=('build', 'run'))
@@ -67,8 +68,15 @@ class PyYt(PythonPackage):
     depends_on("py-scipy", type=('build', 'run'), when="+scipy")
     depends_on("py-setuptools", type="build")
     depends_on("py-sympy", type=('build', 'run'))
+    depends_on("rockstar@yt", type=('build', 'run'), when="+rockstar")
     depends_on("python @2.7:2.999,3.4:")
 
+    @run_before('install')
+    def prep_yt(self):
+        if '+rockstar' in self.spec:
+            with open('rockstar.cfg', 'w') as rockstar_cfg:
+                rockstar_cfg.write(self.spec['rockstar'].prefix)
+
     @run_after('install')
     def check_install(self):
         # The Python interpreter path can be too long for this