Fix mechanism to install Python bindings

Actually, make install already installs Python packages,
so there is no need to do it manually in a post-install hook.

Additionally, we set the DUNE_PY_DIR and DUNE_CONTROL_PATH
environment variables, so that the Python bindings work even
in presence of multiple installations.

packages/dune/package.py

@@ -43,6 +43,7 @@ class Dune(CMakePackage):
 
     # Some variants for customization of Dune
     variant('doc', default=False, description='Build and install documentation')
+    variant('python', default=False, description='Build with Python bindings')
 
     # Variants for upstream dependencies
     variant('arpack', default=True, description='Build ARnoldi PACKage library support')
@@ -71,7 +72,6 @@ class Dune(CMakePackage):
     variant('grid', default=True, description='Build with dune-grid module')
     variant('istl', default=True, description='Build with dune-istl module')
     variant('localfunctions', default=True, description='Build with dune-localfunctions module')
-    variant('python', default=False, description='Build with Python and dune-python')
     variant('spgrid', default=False, description='Build with dune-spgrid module')
     variant('typetree', default=False, description='Build with dune-typetree module')
     variant('uggrid', default=False, description='Build with dune-uggrid module')
@@ -174,7 +174,6 @@ class Dune(CMakePackage):
     depends_on('doxygen', type='build', when='+doc')
     depends_on('gawk')
     depends_on('gmp', when='+gmp')
-    depends_on('imagemagick', type='build', when='+doc')
     depends_on('intel-tbb', when='+tbb')
     depends_on('lapack', when='+lapack')
     depends_on('metis', when='+metis')
@@ -182,10 +181,11 @@ class Dune(CMakePackage):
     depends_on('parmetis', when='+parmetis')
     depends_on('pkg-config', type='build')
     depends_on('python@3.0:', type=('build', 'run'), when='+python')
-    depends_on('py-setuptools', type='build')
+    depends_on('py-setuptools', type='build', when='+python')
     depends_on('py-numpy', type=('build', 'run'), when='+python')
     depends_on('py-pip', type=('build', 'run'), when='+python')
     depends_on('py-sphinx', type=('build', 'run'), when='+doc')
+    depends_on('py-wheel', type='build', when='+python')
     depends_on('scotch+mpi', when='+ptscotch')
     depends_on('sionlib', when='+sionlib')
     depends_on('suite-sparse', when='+suitesparse')
@@ -194,6 +194,22 @@ class Dune(CMakePackage):
     depends_on('zlib', when='+zlib')
     depends_on('zoltan', when='+zoltan')
 
+    def setup_build_environment(self, env):
+        # We reset the DUNE_CONTROL_PATH here because any entries in this
+        # path that contain Dune modules will break the Spack build process.
+        env.set('DUNE_CONTROL_PATH', self.prefix)
+
+    def setup_run_environment(self, env):
+        # Some scripts search the DUNE_CONTROL_PATH for Dune modules (e.g. duneproject).
+        # We need to set it correctly in order to allow multiple simultaneous
+        # installations of the dune package.
+        env.set('DUNE_CONTROL_PATH', self.prefix)
+
+        # Additionally, we need to set the workspace for the Python bindings to something
+        # that is unique to this build of the dune module (it defaults to ~/.cache)
+        if '+python' in self.spec:
+            env.set('DUNE_PY_DIR', self.prefix)
+
     def cmake_args(self):
         """Populate cmake arguments."""
         spec = self.spec
@@ -213,8 +229,10 @@ class Dune(CMakePackage):
         ]
 
         if '+python' in spec:
+            if '@2.7' not in spec:
+                cmake_args.append('-DDUNE_ENABLE_PYTHONBINDINGS:BOOL=TRUE')
             cmake_args.append('-DDUNE_GRID_EXPERIMENTAL_GRID_EXTENSIONS:BOOL=TRUE')
-            cmake_args.append('-DPYTHON_INSTALL_LOCATION:STRING="system"')
+            cmake_args.append('-DDUNE_PYTHON_INSTALL_LOCATION:STRING="system"')
 
         return cmake_args
 
@@ -269,10 +287,3 @@ class Dune(CMakePackage):
         options_file = join_path(self.stage.source_path, "..", "dune.opts")
         installer('--builddir=%s'%self.build_directory ,  '--opts=%s' % options_file, 'make')
 
-    @run_after('install')
-    def install_python_components(self):
-        if '+python' in self.spec:
-            for package in self.python_components:
-                build_directory = 'dune-python/python'
-                with working_dir(join_path(self.build_directory,'dune-python/python')):
-                    setup_py('install', '--prefix={0}'.format(self.prefix))