Move around extension logic

lib/spack/spack/cmd/create.py

@@ -214,6 +214,9 @@ def __call__(self, stage):
 
         self.build_system = build_system
 
+        # Set the appropriate default installation instructions
+        self.install = installDict[build_system]
+
         # Set any necessary extensions for Python and R
         extensions = ''
         if build_system in ['python', 'R']:
@@ -221,9 +224,6 @@ def __call__(self, stage):
 
         self.extends = extensions
 
-        # Set the appropriate default installation instructions
-        self.install = installDict[build_system]
-
 
 def guess_name_and_version(url, args):
     # Try to deduce name and version of the new package from the URL