Add a WafPackage base class (#3975)

* Add a WafPackage base class

* Correct comment in docstring

* Be more specific about the Python versions supported

var/spack/repos/builtin/packages/py-py2cairo/package.py

@@ -25,7 +25,7 @@
 from spack import *
 
 
-class PyPy2cairo(Package):
+class PyPy2cairo(WafPackage):
     """Pycairo is a set of Python bindings for the cairo graphics library."""
 
     homepage = "https://www.cairographics.org/pycairo/"
@@ -35,10 +35,15 @@ class PyPy2cairo(Package):
 
     extends('python')
 
-    depends_on('cairo')
+    depends_on('python', type=('build', 'run'))
+    depends_on('cairo@1.10.0:')
     depends_on('pixman')
+    depends_on('pkg-config', type='build')
 
-    def install(self, spec, prefix):
-        python('waf', 'configure', '--prefix={0}'.format(prefix))
-        python('waf', 'build')
-        python('waf', 'install')
+    # TODO: Add a 'test' deptype
+    # depends_on('py-pytest', type='test')
+
+    def installtest(self):
+        with working_dir('test'):
+            pytest = which('py.test')
+            pytest()