Retry URLs on Networking and PPI functions

[wleoncio]

Summary

The Networking() and PPI() functions use httr::GET() to parse URLs. They only try the URL one time, which sometimes fail due to network errors (a common problem among users with less-than-perfect internet connections). It would be great if these calls were wrapped around loops that try GET some (e.g. 3) times until they get a status_code() of 200, which means a successful URL retrieval.

To-dos

• [x] Create MRE
• [x] Add loop to Networking()
• [x] Add loop to PPI()

MRE

The code below lacks downloading steps for the scripts and data from the Binder.

library("DIscBIO")
source("DIscBIO-CTCs-Binder-Part1.r")
source("DIscBIO-CTCs-Binder-Part2.r")

Networking(data, FileName)
PPI(data, FileName)

[wleoncio]

Using code from DIscBIO-CTCs-Binder-Part1.ipynb and DIscBIO-CTCs-Binder-Part2.ipynb as bases, I'll try to come back to this with an MRE.

Update: Notebooks are bugged and apparently won't be fixed (see issue #30). Trying the full-blown notebook instead.

Update 2: MRE updated to OP.