coverity: report errors when uploading tarball

Curl by default does not report errors by setting the error code.
As the upload can fail through several conditions (e.g. the rate
limit, leading to unauthorized access) we should indicate this
information in Travis CI.

To improve upon the behavior, use `--write-out=%{http_code}` to
write out the HTTP code in addition to the received body and
return an error if the code does not equal 201.

script/coverity.sh

@@ -49,10 +49,24 @@ COVERITY_UNSUPPORTED=1 \
 # Upload results
 tar czf libgit2.tgz cov-int
 SHA=$(git rev-parse --short HEAD)
-curl \
+
+HTML="$(curl \
+	--silent \
+	--write-out "\n%{http_code}" \
 	--form token="$COVERITY_TOKEN" \
 	--form email=bs@github.com \
 	--form file=@libgit2.tgz \
 	--form version="$SHA" \
 	--form description="Travis build" \
-	https://scan.coverity.com/builds?project=libgit2
+	https://scan.coverity.com/builds?project=libgit2)"
+# Body is everything up to the last line
+BODY="$(echo "$HTML" | head -n-1)"
+# Status code is the last line
+STATUS_CODE="$(echo "$HTML" | tail -n1)"
+
+echo "${BODY}"
+
+if [ "${STATUS_CODE}" != "201" ]; then
+	echo "Received error code ${STATUS_CODE} from Coverity"
+	exit 1
+fi