On systems which have already installed nose (perhaps an older version)

importing nose (which is also in Spack's external/ directory) outputs a warning
(since there is more than one nose package). This avoids printing the warning
to the user.

bin/spack

@@ -41,6 +41,14 @@ sys.path.insert(0, SPACK_LIB_PATH)
 SPACK_EXTERNAL_LIBS = os.path.join(SPACK_LIB_PATH, "external")
 sys.path.insert(0, SPACK_EXTERNAL_LIBS)
 
+import warnings
+# Avoid warnings when nose is installed with the python exe being used to run 
+# spack. Note this must be done after Spack's external libs directory is added 
+# to sys.path. 
+with warnings.catch_warnings():
+    warnings.simplefilter("ignore")
+    import nose
+
 # Quick and dirty check to clean orphaned .pyc files left over from
 # previous revisions.  These files were present in earlier versions of
 # Spack, were removed, but shadow system modules that Spack still