function checkForIrregularWhitespace() {
      const source = sourceCode.getText()
      let match
      while ((match = IRREGULAR_WHITESPACE.exec(source)) !== null) {
        errorIndexes.push(match.index)
      }
      while ((match = IRREGULAR_LINE_TERMINATORS.exec(source)) !== null) {
        errorIndexes.push(match.index)
      }
    }
Checks the program source for irregular whitespaces and irregular line terminators
@returns {void}
@private