use_namespace(roxygen=FALSE) creates an invalid NAMESPACE

[mtmorgan]

usethis::create_package("foo", roxygen = FALSE)
devtools::install()

fails with

** building package indices
Error : '\.' is an unrecognized escape in character string starting ""^[^\."
ERROR: installing namespace metadata failed

because

usethis/R/namespace.R

Line 19 in 582a3fa

write_over(path, 'exportPattern("^[^\\.]")')

creates a namespace with text

$ cat NAMESPACE
exportPattern("^[^\.]")

The escaped . needs to be \\\\.