Auto-resolve prefixes to the latest version (#2487)

plugins/python-build/test/test_helper.bash

@@ -139,3 +139,29 @@ assert_output_contains() {
     } | flunk
   }
 }
+
+# Output a modified PATH that ensures that the given executable is not present,
+# but in which system utils necessary for pyenv operation are still available.
+path_without() {
+  local path=":${PATH}:"
+  for exe; do 
+    local found alt util
+    for found in $(PATH="$path" type -aP "$exe"); do
+      found="${found%/*}"
+      if [ "$found" != "${PYENV_ROOT}/shims" ]; then
+        alt="${PYENV_TEST_DIR}/$(echo "${found#/}" | tr '/' '-')"
+        mkdir -p "$alt"
+        for util in bash head cut readlink greadlink; do
+          if [ -x "${found}/$util" ]; then
+            ln -s "${found}/$util" "${alt}/$util"
+          fi
+        done
+        path="${path/:${found}:/:${alt}:}"
+      fi
+    done
+  done
+  path="${path#:}"
+  path="${path%:}"
+  echo "$path"
+}
+