_sanitize_column now reports proper duplicate error

Author: roblevy

pandas/core/frame.py

@@ -1962,6 +1962,8 @@ def _sanitize_column(self, key, value):
                 # GH 4107
                 try:
                     value = value.reindex(self.index).values
+                except ValueError as e:
+                    raise e
                 except:
                     raise TypeError('incompatible index of inserted column '
                                     'with frame index')