Merge pull request #233 from LLNL/bugfix/206-value-error

Fix #206: need to make deps AND root concrete when read in.

lib/spack/spack/directory_layout.py

@@ -212,8 +212,10 @@ def read_spec(self, path):
             spec = Spec.from_yaml(f)
 
         # Specs read from actual installations are always concrete
-        spec._normal = True
-        spec._concrete = True
+        for s in spec.traverse():
+            s._normal = True
+            s._concrete = True
+
         return spec