RF: Use pkgutil to avoid importing nose

Author: effigies

nibabel/optpkg.py

@@ -1,16 +1,13 @@
 """ Routines to support optional packages """
+import pkgutil
 from distutils.version import LooseVersion
-
 from six import string_types
+from .tripwire import TripWire
 
-try:
-    import nose
-except ImportError:
-    have_nose = False
-else:
+if pkgutil.find_loader('nose'):
     have_nose = True
-
-from .tripwire import TripWire
+else:
+    have_nose = False
 
 
 def _check_pkg_version(pkg, min_version):
@@ -121,6 +118,7 @@ def optional_package(name, trip_msg=None, min_version=None):
 
     def setup_module():
         if have_nose:
+            import nose
             raise nose.plugins.skip.SkipTest('No %s for these tests'
                                              % name)
     return pkg, False, setup_module