qemu-iotests: move command line and environment handling from TestRunner to TestEnv

In the next patch, "check" will learn how to execute a test script without
going through TestRunner.  To enable this, keep only the text output
and subprocess handling in the TestRunner; move into TestEnv the logic
to prepare for running a subprocess.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210323181928.311862-4-pbonzini@redhat.com>
Message-Id: <20210503110110.476887-4-pbonzini@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

tests/qemu-iotests/testenv.py

@@ -25,7 +25,7 @@
 import random
 import subprocess
 import glob
-from typing import Dict, Any, Optional, ContextManager
+from typing import List, Dict, Any, Optional, ContextManager
 
 
 def isxfile(path: str) -> bool:
@@ -74,6 +74,21 @@ class TestEnv(ContextManager['TestEnv']):
                      'CACHEMODE_IS_DEFAULT', 'IMGFMT_GENERIC', 'IMGOPTSSYNTAX',
                      'IMGKEYSECRET', 'QEMU_DEFAULT_MACHINE', 'MALLOC_PERTURB_']
 
+    def prepare_subprocess(self, args: List[str]) -> Dict[str, str]:
+        if self.debug:
+            args.append('-d')
+
+        with open(args[0], encoding="utf-8") as f:
+            try:
+                if f.readline().rstrip() == '#!/usr/bin/env python3':
+                    args.insert(0, self.python)
+            except UnicodeDecodeError:  # binary test? for future.
+                pass
+
+        os_env = os.environ.copy()
+        os_env.update(self.get_env())
+        return os_env
+
     def get_env(self) -> Dict[str, str]:
         env = {}
         for v in self.env_variables:

tests/qemu-iotests/testrunner.py

@@ -129,7 +129,6 @@ class TestRunner(ContextManager['TestRunner']):
     def __init__(self, env: TestEnv, makecheck: bool = False,
                  color: str = 'auto') -> None:
         self.env = env
-        self.test_run_env = self.env.get_env()
         self.makecheck = makecheck
         self.last_elapsed = LastElapsedTime('.last-elapsed-cache', env)
 
@@ -243,18 +242,7 @@ def do_run_test(self, test: str) -> TestResult:
             silent_unlink(p)
 
         args = [str(f_test.resolve())]
-        if self.env.debug:
-            args.append('-d')
-
-        with f_test.open(encoding="utf-8") as f:
-            try:
-                if f.readline().rstrip() == '#!/usr/bin/env python3':
-                    args.insert(0, self.env.python)
-            except UnicodeDecodeError:  # binary test? for future.
-                pass
-
-        env = os.environ.copy()
-        env.update(self.test_run_env)
+        env = self.env.prepare_subprocess(args)
 
         t0 = time.time()
         with f_bad.open('w', encoding="utf-8") as f: