popen-context-manager.diff

diff --git a/build/run_tests.py b/build/run_tests.py
index 7ae07806b..d6cf417e1 100755
--- a/build/run_tests.py
+++ b/build/run_tests.py
@@ -91,6 +91,26 @@ class TextColors:
     cls.SUCCESS = ''
 
 
+if hasattr(subprocess.Popen, '__enter__'):
+    Popen = subprocess.Popen
+else:
+    class Popen(subprocess.Popen):
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, type, value, traceback):
+            if self.stdout:
+                self.stdout.close()
+            if self.stderr:
+                self.stderr.close()
+            try:
+                if self.stdin:
+                    self.stdin.close()
+            finally:
+                self.wait()
+
+
 def _get_term_width():
   'Attempt to discern the width of the terminal'
   # This may not work on all platforms, in which case the default of 80
@@ -364,10 +384,10 @@ class TestHarness:
 
     def execute(self, harness):
       start_time = datetime.now()
-      with subprocess.Popen(self._command_line(harness),
-                              stdout=subprocess.PIPE,
-                              stderr=subprocess.PIPE,
-                              cwd=self.progdir) as prog:
+      with Popen(self._command_line(harness),
+                 stdout=subprocess.PIPE,
+                 stderr=subprocess.PIPE,
+                 cwd=self.progdir) as prog:
 
         self.stdout_lines = prog.stdout.readlines()
         self.stderr_lines = prog.stderr.readlines()
@@ -390,24 +410,20 @@ class TestHarness:
     def _count_c_tests(self, progabs, progdir, progbase):
       'Run a c test, escaping parameters as required.'
       cmdline = [ progabs, '--list' ]
-      with subprocess.Popen(cmdline, stdout=subprocess.PIPE,
-                            cwd=progdir) as prog:
+      with Popen(cmdline, stdout=subprocess.PIPE, cwd=progdir) as prog:
         lines = prog.stdout.readlines()
         self.result.append(TestHarness.Job(len(lines) - 2, False, progabs,
                                            progdir, progbase))
-        prog.wait()
 
     def _count_py_tests(self, progabs, progdir, progbase):
       'Run a c test, escaping parameters as required.'
       cmdline = [ sys.executable, progabs, '--list' ]
-      with subprocess.Popen(cmdline, stdout=subprocess.PIPE,
-                            cwd=progdir) as prog:
+      with Popen(cmdline, stdout=subprocess.PIPE, cwd=progdir) as prog:
         lines = prog.stdout.readlines()
 
         for i in range(0, len(lines) - 2):
           self.result.append(TestHarness.Job(i + 1, True, progabs,
                                              progdir, progbase))
-      prog.wait()
 
     def run(self):
       "Run a single test. Return the test's exit code."
@@ -802,8 +818,8 @@ class TestHarness:
       total = len(test_nums)
     else:
       total_cmdline = [cmdline[0], '--list']
-      prog = subprocess.Popen(total_cmdline, stdout=subprocess.PIPE)
-      lines = prog.stdout.readlines()
+      with Popen(total_cmdline, stdout=subprocess.PIPE) as prog:
+        lines = prog.stdout.readlines()
       total = len(lines) - 2
 
     # This has to be class-scoped for use in the progress_func()
@@ -819,23 +835,22 @@ class TestHarness:
       self.dots_written = dots
 
     tests_completed = 0
-    prog = subprocess.Popen(cmdline, stdout=subprocess.PIPE,
-                            stderr=self.log)
-    line = prog.stdout.readline()
-    while line:
-      line = ensure_str(line)
-      if self._process_test_output_line(line):
-        tests_completed += 1
-        progress_func(tests_completed)
-
+    with Popen(cmdline, stdout=subprocess.PIPE, stderr=self.log) as prog:
       line = prog.stdout.readline()
+      while line:
+        line = ensure_str(line)
+        if self._process_test_output_line(line):
+          tests_completed += 1
+          progress_func(tests_completed)
 
-    # If we didn't run any tests, still print out the dots
-    if not tests_completed:
-      os.write(sys.stdout.fileno(), b'.' * dot_count)
+        line = prog.stdout.readline()
 
-    prog.wait()
-    return prog.returncode
+      # If we didn't run any tests, still print out the dots
+      if not tests_completed:
+        os.write(sys.stdout.fileno(), b'.' * dot_count)
+
+      prog.wait()
+      return prog.returncode
 
   def _run_py_test(self, progabs, progdir, progbase, test_nums, dot_count):
     'Run a python test, passing parameters as needed.'