Test NumPy blas flag before reusing them. Sometimes the dev package

theano/tensor/blas.py

@@ -261,7 +261,7 @@ SOMEPATH/Canopy_64bit/User/lib/python2.7/site-packages/numpy/distutils/system_in
         #if numpy was linked with library that are not installed, we
         #can't reuse them.
         if any(os.path.exists(dir) for dir in blas_info['library_dirs']):
-            return ' '.join(
+            ret = (
                 #TODO: the Gemm op below should separate the
                 # -L and -l arguments into the two callbacks
                 # that CLinker uses for that stuff.  for now,
@@ -271,6 +271,12 @@ SOMEPATH/Canopy_64bit/User/lib/python2.7/site-packages/numpy/distutils/system_in
                 ['-l%s' % l for l in blas_info['libraries']] +
                 [])
 #               ['-I%s' % l for l in blas_info['include_dirs']])
+            #if numpy was linked with library that are not installed or
+            #the dev version of the package is not currently available, we
+            #can't reuse them.
+            if GCC_compiler.try_flags(ret):
+                return ' '.join(ret)
+
     except KeyError:
         pass