[BUG] summarize() enters infinite loop when interval=0 and alignToFrom=True

[jonnangle]

Describe the bug If you set interval=0 and alignToFrom=True when using summarize(), graphite-web enters an infinite loop.

NB:

• this can also happen inadvertently if you accidentally provide an unquoted string as the interval that then gets parsed as 0.
• when alignToFrom=false, the infinite loop is avoided due to a ZeroDivisionError.

To Reproduce Steps to reproduce the behavior:

Render a target summarize(some.metric, 0, "sum", true). The process spins on CPU and grows until memory is exhausted.

Expected behavior Receive a suitable error message.

Environment (please complete the following information):

• OS flavor: Amazon Linux 2
• Graphite-web version: 1.1.10
• Django/Python version: 1.11/2.7
• Setup type: pip