ENH: Use pkgutil.find_loader to avoid loading modules on __init__

Author: effigies

nipype/interfaces/base/core.py

@@ -1164,12 +1164,10 @@ class LibraryBaseInterface(BaseInterface):
     def __init__(self, check_import=True, *args, **kwargs):
         super(LibraryBaseInterface, self).__init__(*args, **kwargs)
         if check_import:
-            import importlib
+            import pkgutil
             failed_imports = []
             for pkg in (self._pkg,) + tuple(self.imports):
-                try:
-                    importlib.import_module(pkg)
-                except ImportError:
+                if pkgutil.find_loader(pkg) is None:
                     failed_imports.append(pkg)
             if failed_imports:
                 iflogger.warning('Unable to import %s; %s interface may fail to '