Measure the width of each table column.

def table_measure(self, columns, content):
        """
        Measure the width of each table column.
        """
        dimensions = {}
        for row in content:
            i = 0
            for cell in row:
                # Calculate maximum from:
                dimensions[i] = max(
                        dimensions.get(i, 0),              # current column max width
                        len(cell),                         # current cell value width
                        len(columns[i].get('label', '')),  # column label width
                        columns[i].get('width_min', 0),    # configured column minimal width
                    )
                i += 1
        return dimensions