Update cray-libsci homepage and install error (#18581)

var/spack/repos/builtin/packages/cray-libsci/package.py

@@ -2,7 +2,6 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
-from spack.concretize import NoBuildError
 from spack.util.module_cmd import module
 from spack.util.module_cmd import get_path_args_from_module_line
 
@@ -11,8 +10,8 @@ class CrayLibsci(Package):
     """The Cray Scientific Libraries package, LibSci, is a collection of
     numerical routines optimized for best performance on Cray systems."""
 
-    homepage = "http://www.nersc.gov/users/software/programming-libraries/math-libraries/libsci/"
-    url      = "http://www.nersc.gov/users/software/programming-libraries/math-libraries/libsci/"
+    homepage = "https://docs.nersc.gov/development/libraries/libsci/"
+    has_code = False    # Skip attempts to fetch source that is not available
 
     version("18.11.1.2")
     version("16.11.1")
@@ -78,4 +77,6 @@ def scalapack_libs(self):
         return self.blas_libs
 
     def install(self, spec, prefix):
-        raise NoBuildError(spec)
+        raise InstallError(
+            self.spec.format('{name} is not installable, you need to specify '
+                             'it as an external package in packages.yaml'))