Migrate check_elf_file.py to python3

Also, create a python_binary_host so that it runs using the hermetic
python toolchain.

Test: m check-elf-files
Bug: 203436762
Change-Id: I964342a27f6b6c9dcdbbe910d4dc6c9ec00c2213

core/config.mk

@@ -612,7 +612,7 @@ TUNE2FS := $(HOST_OUT_EXECUTABLES)/tune2fs$(HOST_EXECUTABLE_SUFFIX)
 JARJAR := $(HOST_OUT_JAVA_LIBRARIES)/jarjar.jar
 DATA_BINDING_COMPILER := $(HOST_OUT_JAVA_LIBRARIES)/databinding-compiler.jar
 FAT16COPY := build/make/tools/fat16copy.py
-CHECK_ELF_FILE := build/make/tools/check_elf_file.py
+CHECK_ELF_FILE := $(HOST_OUT_EXECUTABLES)/check_elf_file$(HOST_EXECUTABLE_SUFFIX)
 LPMAKE := $(HOST_OUT_EXECUTABLES)/lpmake$(HOST_EXECUTABLE_SUFFIX)
 ADD_IMG_TO_TARGET_FILES := $(HOST_OUT_EXECUTABLES)/add_img_to_target_files$(HOST_EXECUTABLE_SUFFIX)
 BUILD_IMAGE := $(HOST_OUT_EXECUTABLES)/build_image$(HOST_EXECUTABLE_SUFFIX)

tools/Android.bp

@@ -59,3 +59,8 @@ python_binary_host {
   name: "check_radio_versions",
   srcs: ["check_radio_versions.py"],
 }
+
+python_binary_host {
+  name: "check_elf_file",
+  srcs: ["check_elf_file.py"],
+}

tools/check_elf_file.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (C) 2019 The Android Open Source Project
 #
@@ -196,11 +196,7 @@ class ELFParser(object):
   def _read_llvm_readobj(cls, elf_file_path, header, llvm_readobj):
     """Run llvm-readobj and parse the output."""
     cmd = [llvm_readobj, '--dynamic-table', '--dyn-symbols', elf_file_path]
-    proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-    out, _ = proc.communicate()
-    rc = proc.returncode
-    if rc != 0:
-      raise subprocess.CalledProcessError(rc, cmd, out)
+    out = subprocess.check_output(cmd, text=True)
     lines = out.splitlines()
     return cls._parse_llvm_readobj(elf_file_path, header, lines)
 
@@ -467,7 +463,7 @@ class Checker(object):
     """Check whether all undefined symbols are resolved to a definition."""
     all_elf_files = [self._file_under_test] + self._shared_libs
     missing_symbols = []
-    for sym, imported_vers in self._file_under_test.imported.iteritems():
+    for sym, imported_vers in self._file_under_test.imported.items():
       for imported_ver in imported_vers:
         lib = self._find_symbol_from_libs(all_elf_files, sym, imported_ver)
         if not lib: