FIX: treat filename=None correctly

src/caosadvancedtools/table_importer.py

@@ -73,10 +73,9 @@ class XLS_Importer(object):
         try:
             xls_file = pd.io.excel.ExcelFile(filename)
         except XLRDError as e:
-            errmsg = ("Cannot read {}.".format(filename) if "\n"+filename+"\n"
-                      else "the file.")
             logger.warning(
-                errmsg,
+                "Cannot read \n{}.\nError:{}".format(filename,
+                                                     str(e)),
                 extra={'identifier': str(filename),
                        'category': "inconsistency"})
             raise DataInconsistencyError(*e.args)
@@ -91,10 +90,8 @@ class XLS_Importer(object):
         try:
             df = xls_file.parse(converters=self.converters)
         except Exception as e:
-            errmsg = ("Cannot parse {}.".format(filename) if "\n"+filename+"\n"
-                      else "the file.")
             logger.warning(
-                errmsg,
+                "Cannot parse {}.".format(filename),
                 extra={'identifier': str(filename),
                        'category': "inconsistency"})
             raise DataInconsistencyError(*e.args)
@@ -111,7 +108,7 @@ class XLS_Importer(object):
         for col in self.required_columns:
             if col not in df.columns:
                 errmsg = "Column '{}' missing in ".format(col)
-                errmsg += ("{}.".format(filename) if "\n"+filename+"\n"
+                errmsg += ("\n{}.\n".format(filename) if filename
                            else "the file.")
                 errmsg += "Stopping to treat this file..."
                 logger.warning(