Backport PR #4217: avoid importing numpy at the module level

in utils.pickleutil

With this change, numpy is not in sys.modules at kernel startup.

IPython/utils/pickleutil.py

@@ -25,11 +25,6 b' try:'
 except ImportError:
     import pickle
 
-try:
-    import numpy
-except:
-    numpy = None
-
 import codeutil  # This registers a hook when it's imported
 import py3compat
 from importstring import import_item
@@ -163,6 +158,7 b' class CannedClass(CannedObject):'
 
 class CannedArray(CannedObject):
     def __init__(self, obj):
+        from numpy import ascontiguousarray
         self.shape = obj.shape
         self.dtype = obj.dtype.descr if obj.dtype.fields else obj.dtype.str
         if sum(obj.shape) == 0:
@@ -170,16 +166,17 b' class CannedArray(CannedObject):'
             self.buffers = [pickle.dumps(obj, -1)]
         else:
             # ensure contiguous
-            obj = numpy.ascontiguousarray(obj, dtype=None)
+            obj = ascontiguousarray(obj, dtype=None)
             self.buffers = [buffer(obj)]
     
     def get_object(self, g=None):
+        from numpy import frombuffer
         data = self.buffers[0]
         if sum(self.shape) == 0:
             # no shape, we just pickled it
             return pickle.loads(data)
         else:
-            return numpy.frombuffer(data, dtype=self.dtype).reshape(self.shape)
+            return frombuffer(data, dtype=self.dtype).reshape(self.shape)
 
 
 class CannedBytes(CannedObject):
@@ -225,7 +222,7 b' def _import_mapping(mapping, original=None):'
             except Exception:
                 if original and key not in original:
                     # only message on user-added classes
-                    log.error("cannning class not importable: %r", key, exc_info=True)
+                    log.error("canning class not importable: %r", key, exc_info=True)
                 mapping.pop(key)
             else:
                 mapping[cls] = mapping.pop(key)