COMPAT: Add back remove_na for seaborn

Closes gh-16971.

pandas/core/dtypes/missing.py

@@ -2,6 +2,8 @@
 missing types & inference
 """
 import numpy as np
+import warnings
+
 from pandas._libs import lib
 from pandas._libs.tslib import NaT, iNaT
 from .generic import (ABCMultiIndex, ABCSeries,
@@ -401,3 +403,16 @@ def remove_na_arraylike(arr):
     Return array-like containing only true/non-NaN values, possibly empty.
     """
     return arr[notnull(lib.values_from_object(arr))]
+
+
+# see gh-16971
+def remove_na(arr):
+    """
+    DEPRECATED : this function will be removed in a future version.
+
+    Alias to `remove_na_arraylike` for `seaborn` compatibility.
+    """
+
+    warnings.warn("remove_na is deprecated. Use remove_na_arraylike instead.",
+                  FutureWarning, stacklevel=2)
+    return remove_na_arraylike(arr)

pandas/core/series.py

@@ -38,6 +38,9 @@
     maybe_cast_to_datetime, maybe_castable)
 from pandas.core.dtypes.missing import isnull, notnull, remove_na_arraylike
 
+# see gh-16971
+from pandas.core.dtypes.missing import remove_na  # noqa
+
 from pandas.core.common import (is_bool_indexer,
                                 _default_index,
                                 _asarray_tuplesafe,

pandas/tests/dtypes/test_missing.py

@@ -14,7 +14,13 @@
 from pandas.core.dtypes.dtypes import DatetimeTZDtype
 from pandas.core.dtypes.missing import (
     array_equivalent, isnull, notnull,
-    na_value_for_dtype)
+    na_value_for_dtype, remove_na)
+
+
+def test_remove_na_deprecation():
+    # see gh-16971
+    with tm.assert_produces_warning(FutureWarning):
+        remove_na(Series([]))
 
 
 def test_notnull():