added 'test_concat_date_col_fail' test

Author: anmyachev

pandas/_libs/tslibs/parsing.pyx

@@ -58,8 +58,6 @@ _DEFAULT_DATETIME = datetime(1, 1, 1).replace(hour=0, minute=0,
 cdef:
     set _not_datelike_strings = {'a', 'A', 'm', 'M', 'p', 'P', 't', 'T'}
 
-    set _not_datelike_strings = {'a', 'A', 'm', 'M', 'p', 'P', 't', 'T'}
-
 # ----------------------------------------------------------------------
 cdef:
     const char* delimiters = " /-."

pandas/tests/io/parser/test_parse_dates.py

@@ -19,12 +19,11 @@
 from pandas.compat.numpy import np_array_datetime64_compat
 
 import pandas as pd
-from pandas import DataFrame, DatetimeIndex, Index, MultiIndex
+from pandas import DataFrame, DatetimeIndex, Index, MultiIndex, Series
 from pandas.core.indexes.datetimes import date_range
 import pandas.util.testing as tm
 
 import pandas.io.date_converters as conv
-import pandas.io.parsers as parsers
 
 # constant
 _DEFAULT_DATETIME = datetime(1, 1, 1)
@@ -117,6 +116,18 @@ def date_parser(*date_cols):
     tm.assert_frame_equal(result, expected)
 
 
+@pytest.mark.parametrize("container", [list, tuple, Index, Series])
+@pytest.mark.parametrize("dim", [1, 2])
+def test_concat_date_col_fail(container, dim):
+    msg = "not all elements from date_cols are numpy arrays"
+    value = "19990127"
+
+    date_cols = tuple(container([value]) for _ in range(dim))
+
+    with pytest.raises(ValueError, match=msg):
+        parsing._concat_date_cols(date_cols)
+
+
 @pytest.mark.parametrize("keep_date_col", [True, False])
 def test_multiple_date_col(all_parsers, keep_date_col):
     data = """\