Don't test process_vm_readv on Travis arches that use qemu

CONTRIBUTING.md

@@ -88,9 +88,11 @@ locally.  More information is available in the [CI Readme][ci-readme].
 ### Disabling a test in the CI environment
 
 Sometimes there are features that cannot be tested in the CI environment.
-To stop a test from running under CI, add `#[cfg_attr(travis, ignore)]`
-to it. Please include a comment describing the reason it shouldn't run
-under CI, and a link to an upstream issue if possible!
+To stop a test from causing a CI failure, add `#[cfg_attr(travis, ignore)]`
+to it. To prevent it from running entirely (in case the test process is
+dying), add `#[cfg(not(travis))]`.  Please include a comment describing
+the reason it shouldn't run under CI, and a link to an upstream issue if
+possible!
 
 ## bors, the bot who merges all the PRs
 

test/sys/test_uio.rs

@@ -193,6 +193,8 @@ fn test_preadv() {
 
 #[test]
 #[cfg(any(target_os = "linux", target_os = "android"))]
+// qemu-user does not yet implement process_vm_readv, cf. PR #568
+#[cfg(not(all(travis, any(target_arch = "arm", target_arch = "aarch64"))))]
 fn test_process_vm_readv() {
     use nix::unistd::ForkResult::*;
     use nix::sys::signal::*;