Incorrectly checks xpath and returns an error when publishing

[bw4sz]

The local path checker is a bit overzealous and mistakes parsing of xml as the user trying to read in data. For example
I am interacting with a web API. I then need to do some parsing of the xml.

 r<-wcPOST()
  start_epoch <- as.numeric(now() - lubridate::days(days_lag))
  
  #Get program number
  xpath <- paste("//data/deployment/argos/last_uplink_date", 
                 "[number() > number(", start_epoch, ")]/../program_number", sep = "")
  program_number <- XML::xpathSApply(XML::xmlParse(content(r,"text")), xpath, XML::xmlValue)

yields

This all works great locally and hosted. Note there is no interaction with the local file system. But when I go to publish I get. "Paths should be to files within the project directory". I can force a 'yes' to override the check, but it could be improved.

Thanks.

[hadley]

Closely related to #611

[hadley]

Filter if the file exists — no easy way to do that because there's no actual path constructed by this linter.