more helpful error msg when calling read.Conllu files=""

Author: martinpopel

udapi/core/files.py

@@ -43,6 +43,8 @@ def __init__(self, filenames=None, filehandle=None, encoding='utf-8'):
  elif isinstance(filenames, list):
  self.filenames = filenames
  elif isinstance(filenames, str):
+ if filenames == '':
+ raise ValueError('Filenames (files=) cannot be an empty string')
  self.filenames = self.string_to_filenames(filenames)
  else:
  raise ValueError('Parameter "filenames" must be a list or str')