use python:alpine as musllinux test image

docker_test_wrap.sh

@@ -2,6 +2,17 @@
 # Install and test steps on Linux
 set -e
 
+# shim for python:alpine not having bash
+if [ -f "/etc/alpine-release" ]; then
+  apk update
+  apk add bash
+fi
+
+if [ -z "$BASH" ]; then
+  bash $0 $@
+  exit $?
+fi
+
 # "python" and "pip" are already on the path as part of the docker
 # startup code in choose_python.sh, but the following are required and not
 # necessarily already set
@@ -10,7 +21,7 @@ PYTHON_EXE=${PYTHON_EXE:-python}
 PIP_CMD=${PIP_CMD:-pip}
 
 # Get needed utilities
-MULTIBUILD_DIR=$(dirname "${BASH_SOURCE[0]}")
+MULTIBUILD_DIR=$(dirname "$0")
 source $MULTIBUILD_DIR/common_utils.sh
 
 # Change into root directory of repo

travis_linux_steps.sh

@@ -111,6 +111,7 @@ function install_run {
     # Depends on
     #  PLAT (can be passed in as argument)
     #  MB_PYTHON_VERSION
+    #  MB_ML_LIBC (optional)
     #  UNICODE_WIDTH (optional)
     #  WHEEL_SDIR (optional)
     #  MANYLINUX_URL (optional)
@@ -118,8 +119,12 @@ function install_run {
     #  MB_TEST_VER (optional)
     local plat=${1:-${PLAT:-x86_64}}
     if [ -z "$DOCKER_TEST_IMAGE" ]; then
+        if [ "$MB_ML_LIBC" == "musllinux" ]; then
+          local docker_image="python:$MB_PYTHON_VERSION-alpine"
+        else
           local bitness=$([ "$plat" == i686 ] && echo 32 || echo 64)
           local docker_image="matthewbrett/trusty:$bitness"
+        fi
     else
         # aarch64 is called arm64v8 in Ubuntu
         local plat_subst=$([ "$plat" == aarch64 ] && echo arm64v8 || echo $plat)
@@ -135,5 +140,6 @@ function install_run {
         -e MANYLINUX_URL="$MANYLINUX_URL" \
         -e TEST_DEPENDS="$TEST_DEPENDS" \
         -v $PWD:/io \
+        --entrypoint sh \
         $docker_image /io/$MULTIBUILD_DIR/docker_test_wrap.sh
 }