Issue with real_path on mapped network drive

Having an issue discussed originally in https://github.com/jdblischak/workflowr/issues/219 which looks similar, but not identical to https://github.com/r-lib/fs/issues/223

Under Windows on network-mounted drives, path_real() triggers an Illegal Operation, using both the fs version from Github and via CRAN.

Minimal example:

> library(fs)
> path_wd()
//uniwa.uwa.edu.au/userhome/staff3/<STAFFID>/My Documents
> dir_create("testDir")
> dir_exists("testDir")
testDir 
   TRUE 
> path_real("testDir")
Error: [EISDIR] Failed to realize 'testDir': illegal operation on a directory
> dir_delete("testDir")

and a traceback:

> path_real('testDir')
Error: [ENOENT] Failed to realize 'testDir': no such file or directory
> traceback()
2: (function (..., call. = TRUE, domain = NULL) 
   {
       args <- list(...)
       if (length(args) == 1L && inherits(args[[1L]], "condition")) {
           cond <- args[[1L]]
           if (nargs() > 1L) 
               warning("additional arguments ignored in stop()")
           message <- conditionMessage(cond)
           call <- conditionCall(cond)
           .Internal(.signalCondition(cond, message, call))
           .Internal(.dfltStop(message, call))
       }
       else .Internal(stop(call., .makeMessage(..., domain = domain)))
   })(list(message = "[ENOENT] Failed to realize 'testDir': no such file or directory"))
1: path_real("testDir")

SessionInfo:

R version 3.6.3 (2020-02-29)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

Matrix products: default

Random number generation:
 RNG:     Mersenne-Twister 
 Normal:  Inversion 
 Sample:  Rounding 

locale:
[1] LC_COLLATE=English_Australia.1252  LC_CTYPE=English_Australia.1252    LC_MONETARY=English_Australia.1252 LC_NUMERIC=C                      
[5] LC_TIME=English_Australia.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] fs_1.5.0.9000

loaded via a namespace (and not attached):
 [1] compiler_3.6.3  magrittr_1.5    ellipsis_0.3.1  tools_3.6.3     pillar_1.4.4    rstudioapi_0.11 tibble_3.0.2    yaml_2.2.1      crayon_1.3.4   
[10] vctrs_0.3.1     lifecycle_0.2.0 pkgconfig_2.0.3 rlang_0.4.6

r-lib / fs

Issue with real_path on mapped network drive #296