import re


def VerifyTabs(filename, lines):
  """Checks to make sure the file has no tab characters.

  Args:
    filename: the file under consideration as string
    lines: contents of the file as string array

  Returns:
    A list of tuples with format [(line_number, msg), ...] with any violations
    found.
  """
  lint = []
  tab_re = re.compile(r'\t')
  line_num = 1
  for line in lines:
    if tab_re.match(line.rstrip('\n')):
      lint.append((filename, line_num, 'Tab found instead of whitespace'))
    line_num += 1
  return lint