Fix error message to actually use python string formatting
Fix error message to actually use python string formatting

This is using printf-style formatting, which Python happily accepts and
ignores.

Part of #1750: now, instead of printing

```
xcode_configure.bzl:57:5: Invoking xcodebuild failed, return code %s,
stderr: %s 1
```

it prints:

```
xcode_configure.bzl:57:5: Invoking xcodebuild failed, return code 1,
stderr: xcrun: error: missing DEVELOPER_DIR path:  E.g. no application
claims the file"
```

Closes #1751.

--
Reviewed-on: https://github.com/bazelbuild/bazel/pull/1751
MOS_MIGRATED_REVID=132884125

dslomov/bazel-windows,kchodorow/bazel,twitter-forks/bazel,mbrukman/bazel,ButterflyNetwork/bazel,damienmg/bazel,mrdomino/bazel,aehlig/bazel,meteorcloudy/bazel,katre/bazel,Asana/bazel,spxtr/bazel,spxtr/bazel,snnn/bazel,kchodorow/bazel,juhalindfors/bazel-patches,mikelikespie/bazel,variac/bazel,damienmg/bazel,aehlig/bazel,juhalindfors/bazel-patches,variac/bazel,twitter-forks/bazel,werkt/bazel,damienmg/bazel,LuminateWireless/bazel,Asana/bazel,twitter-forks/bazel,dslomov/bazel-windows,mbrukman/bazel,aehlig/bazel,mrdomino/bazel,kchodorow/bazel,LuminateWireless/bazel,zhexuany/bazel,dropbox/bazel,akira-baruah/bazel,twitter-forks/bazel,akira-baruah/bazel,katre/bazel,ButterflyNetwork/bazel,dslomov/bazel,meteorcloudy/bazel,cushon/bazel,bazelbuild/bazel,werkt/bazel,damienmg/bazel,hermione521/bazel,iamthearm/bazel,kchodorow/bazel-1,spxtr/bazel,mikelikespie/bazel,perezd/bazel,ButterflyNetwork/bazel,safarmer/bazel,Asana/bazel,mikelikespie/bazel,aehlig/bazel,ulfjack/bazel,katre/bazel,kchodorow/bazel-1,meteorcloudy/bazel,juhalindfors/bazel-patches,davidzchen/bazel,ButterflyNetwork/bazel,snnn/bazel,mbrukman/bazel,variac/bazel,hermione521/bazel,perezd/bazel,akira-baruah/bazel,zhexuany/bazel,juhalindfors/bazel-patches,katre/bazel,juhalindfors/bazel-patches,dropbox/bazel,hermione521/bazel,zhexuany/bazel,meteorcloudy/bazel,meteorcloudy/bazel,spxtr/bazel,hermione521/bazel,Asana/bazel,aehlig/bazel,iamthearm/bazel,dropbox/bazel,bazelbuild/bazel,twitter-forks/bazel,werkt/bazel,twitter-forks/bazel,davidzchen/bazel,safarmer/bazel,iamthearm/bazel,dslomov/bazel-windows,dropbox/bazel,dslomov/bazel,mrdomino/bazel,safarmer/bazel,snnn/bazel,aehlig/bazel,safarmer/bazel,davidzchen/bazel,zhexuany/bazel,davidzchen/bazel,werkt/bazel,zhexuany/bazel,kchodorow/bazel,bazelbuild/bazel,Asana/bazel,perezd/bazel,akira-baruah/bazel,kchodorow/bazel-1,davidzchen/bazel,cushon/bazel,akira-baruah/bazel,kchodorow/bazel,ulfjack/bazel,juhalindfors/bazel-patches,snnn/bazel,ButterflyNetwork/bazel,dslomov/bazel,mikelikespie/bazel,variac/bazel,perezd/bazel,LuminateWireless/bazel,kchodorow/bazel,bazelbuild/bazel,perezd/bazel,hermione521/bazel,meteorcloudy/bazel,werkt/bazel,variac/bazel,ulfjack/bazel,dslomov/bazel-windows,werkt/bazel,hermione521/bazel,cushon/bazel,mikelikespie/bazel,dslomov/bazel-windows,damienmg/bazel,mbrukman/bazel,Asana/bazel,iamthearm/bazel,davidzchen/bazel,dropbox/bazel,variac/bazel,spxtr/bazel,iamthearm/bazel,snnn/bazel,iamthearm/bazel,cushon/bazel,ulfjack/bazel,aehlig/bazel,mrdomino/bazel,Asana/bazel,dslomov/bazel-windows,twitter-forks/bazel,kchodorow/bazel-1,mbrukman/bazel,LuminateWireless/bazel,perezd/bazel,damienmg/bazel,katre/bazel,safarmer/bazel,dslomov/bazel,bazelbuild/bazel,ButterflyNetwork/bazel,zhexuany/bazel,mrdomino/bazel,mrdomino/bazel,ulfjack/bazel,kchodorow/bazel-1,dslomov/bazel,akira-baruah/bazel,safarmer/bazel,LuminateWireless/bazel,dslomov/bazel,bazelbuild/bazel,kchodorow/bazel,dslomov/bazel,dropbox/bazel,spxtr/bazel,perezd/bazel,juhalindfors/bazel-patches,ulfjack/bazel,snnn/bazel,mikelikespie/bazel,davidzchen/bazel,katre/bazel,cushon/bazel,kchodorow/bazel-1,LuminateWireless/bazel,variac/bazel,ulfjack/bazel,cushon/bazel,meteorcloudy/bazel,spxtr/bazel,mbrukman/bazel,snnn/bazel,damienmg/bazel