ERR: correctly raise ValueError on empty input to pd.eval() and df.query() (#13139)

Author: tserafim

doc/source/whatsnew/v0.19.1.txt

@@ -57,4 +57,4 @@ Bug Fixes
 
 - Bug in ``pd.pivot_table`` may raise ``TypeError`` or ``ValueError`` when ``index`` or ``columns``
   is not scalar and ``values`` is not specified (:issue:`14380`)
-- pd.eval('') and df.query('') now show better error message and raise ``ValueError`` (:issue: `13139`)
+- corrrecly raise ``ValueError`` on empty input to pd.eval() and df.query() (:issue: `13139`)

pandas/computation/tests/test_eval.py

@@ -1892,6 +1892,7 @@ def test_bad_resolver_raises():
 
 
 def check_empty_string_raises(engine, parser):
+    # GH 13139
     tm.skip_if_no_ne(engine)
     with tm.assertRaisesRegexp(ValueError, 'expr cannot be an empty string'):
         pd.eval('', engine=engine, parser=parser)