add deprecation warning for imports from pandas.tools.merge for concat

pandas/tools/merge.py

@@ -10,6 +10,7 @@
 from pandas.compat import range, lzip, zip, map, filter
 import pandas.compat as compat
 
+import pandas as pd
 from pandas import (Categorical, Series, DataFrame,
                     Index, MultiIndex, Timedelta)
 from pandas.core.frame import _merge_doc
@@ -40,6 +41,20 @@
 import pandas.hashtable as _hash
 
 
+# back-compat of pseudo-public API
+def concat_wrap():
+
+    def wrapper(*args, **kwargs):
+        warnings.warn("pandas.tools.merge.concat is deprecated. "
+                      "import from the public API: "
+                      "pandas.concat instead",
+                      FutureWarning, stacklevel=3)
+        return pd.concat(*args, **kwargs)
+    return wrapper
+
+concat = concat_wrap()
+
+
 @Substitution('\nleft : DataFrame')
 @Appender(_merge_doc, indents=0)
 def merge(left, right, how='inner', on=None, left_on=None, right_on=None,