Fix mkl warning in default_blas_ldflags

tests/test_config.py

 """
 Test config options.
 """
+import logging
+from unittest.mock import patch
 
+from theano.configdefaults import default_blas_ldflags
 from theano.configparser import THEANO_FLAGS_DICT, AddConfigVar, ConfigParam
 
 
-class TestConfig:
-    def test_invalid_default(self):
+def test_invalid_default():
     # Ensure an invalid default value found in the Theano code only causes
     # a crash if it is not overridden by the user.
 
@@ -43,3 +45,16 @@ class TestConfig:
     assert "T_config.test_invalid_default_b" not in THEANO_FLAGS_DICT
 
     # TODO We should remove these dummy options on test exit.
+
+
+@patch("theano.configdefaults.try_blas_flag", return_value=None)
+@patch("theano.configdefaults.sys")
+def test_default_blas_ldflags(sys_mock, try_blas_flag_mock, caplog):
+
+    sys_mock.version = "3.8.0 | packaged by conda-forge | (default, Nov 22 2019, 19:11:38) \n[GCC 7.3.0]"
+
+    with patch.dict("sys.modules", {"mkl": None}):
+        with caplog.at_level(logging.WARNING):
+            default_blas_ldflags()
+
+    assert "install mkl with" in caplog.text

theano/configdefaults.py

@@ -1835,7 +1835,7 @@ def default_blas_ldflags():
         # the fallback and test -lblas could give slow computation, so
         # warn about this.
         for warn in warn_record:
-            _logger.warning(*warn)
+            _logger.warning(warn)
         del warn_record
 
         # Some environment don't have the lib dir in LD_LIBRARY_PATH.