sigpipe-remote: check for python version earlier in the script

The should abort early, using the wrong python is a pretty bad sign.

Differential Revision: https://phab.mercurial-scm.org/D11078

tests/testlib/sigpipe-remote.py

@@ -1,152 +1,152 b''
 #!/usr/bin/env python3
 from __future__ import print_function
 
 import io
 import os
 import subprocess
 import sys
 import time
 
-# we cannot use mercurial.testing as long as python2 is not dropped as the test will only install the mercurial module for python2 in python2 run
+# we cannot use mercurial.testing as long as python2 is not dropped as the test
+# will only install the mercurial module for python2 in python2 run
+if sys.version_info[0] < 3:
+    print('SIGPIPE-HELPER: script should run with Python 3', file=sys.stderr)
+    sys.exit(255)
 
 if isinstance(sys.stdout.buffer, io.BufferedWriter):
     print('SIGPIPE-HELPER: script need unbuffered output', file=sys.stderr)
     sys.exit(255)
 
 DEBUG_FILE = os.environ.get('SIGPIPE_REMOTE_DEBUG_FILE')
 if DEBUG_FILE is None:
     debug_stream = sys.stderr.buffer
 else:
     debug_stream = open(DEBUG_FILE, 'bw', buffering=0)
 
 SYNCFILE1 = os.environ.get('SYNCFILE1')
 SYNCFILE2 = os.environ.get('SYNCFILE2')
 if SYNCFILE1 is None:
     print('SIGPIPE-HELPER: missing variable $SYNCFILE1', file=sys.stderr)
     sys.exit(255)
 if SYNCFILE2 is None:
     print('SIGPIPE-HELPER: missing variable $SYNCFILE2', file=sys.stderr)
     sys.exit(255)
 
 
 def _timeout_factor():
     """return the current modification to timeout"""
     default = int(os.environ.get('HGTEST_TIMEOUT_DEFAULT', 360))
     current = int(os.environ.get('HGTEST_TIMEOUT', default))
     if current == 0:
         return 1
     return current / float(default)
 
 
 def wait_file(path, timeout=10):
     timeout *= _timeout_factor()
     start = time.time()
     while not os.path.exists(path):
         if (time.time() - start) > timeout:
             raise RuntimeError(b"timed out waiting for file: %s" % path)
         time.sleep(0.01)
 
 
 def write_file(path, content=b''):
     with open(path, 'wb') as f:
         f.write(content)
 
 
 # end of mercurial.testing content
 
-if sys.version_info[0] < 3:
-    print('SIGPIPE-HELPER: script should run with Python 3', file=sys.stderr)
-    sys.exit(255)
-
 
 def sysbytes(s):
     return s.encode('utf-8')
 
 
 def sysstr(s):
     return s.decode('latin-1')
 
 
 debug_stream.write(b'SIGPIPE-HELPER: Starting\n')
 
 TESTLIB_DIR = os.path.dirname(sys.argv[0])
 WAIT_SCRIPT = os.path.join(TESTLIB_DIR, 'wait-on-file')
 
 hooks_cmd = '%s 10 %s %s'
 hooks_cmd %= (
     WAIT_SCRIPT,
     SYNCFILE2,
     SYNCFILE1,
 )
 
 try:
     cmd = ['hg']
     cmd += sys.argv[1:]
     sub = subprocess.Popen(
         cmd,
         bufsize=0,
         close_fds=True,
         stdin=sys.stdin,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
     )
 
     basedir = os.path.dirname(sys.argv[0])
     worker = os.path.join(basedir, 'sigpipe-worker.py')
 
     cmd = [sys.executable, worker]
 
     stdout_worker = subprocess.Popen(
         cmd,
         bufsize=0,
         close_fds=True,
         stdin=sub.stdout,
         stdout=sys.stdout,
         stderr=sys.stderr,
     )
 
     stderr_worker = subprocess.Popen(
         cmd,
         bufsize=0,
         close_fds=True,
         stdin=sub.stderr,
         stdout=sys.stderr,
         stderr=sys.stderr,
     )
     debug_stream.write(b'SIGPIPE-HELPER: Redirection in place\n')
     os.close(sub.stdout.fileno())
     os.close(sub.stderr.fileno())
     debug_stream.write(b'SIGPIPE-HELPER: pipes closed in main\n')
 
     try:
         wait_file(sysbytes(SYNCFILE1))
     except RuntimeError as exc:
         msg = sysbytes(str(exc))
         debug_stream.write(b'SIGPIPE-HELPER: wait failed: %s\n' % msg)
     else:
         debug_stream.write(b'SIGPIPE-HELPER: SYNCFILE1 detected\n')
     stdout_worker.kill()
     stderr_worker.kill()
     stdout_worker.wait(10)
     stderr_worker.wait(10)
     debug_stream.write(b'SIGPIPE-HELPER: worker killed\n')
 
     debug_stream.write(b'SIGPIPE-HELPER: creating SYNCFILE2\n')
     write_file(sysbytes(SYNCFILE2))
 finally:
     debug_stream.write(b'SIGPIPE-HELPER: Shutting down\n')
     if not sys.stdin.closed:
         sys.stdin.close()
     try:
         sub.wait(timeout=30)
     except subprocess.TimeoutExpired:
         msg = b'SIGPIPE-HELPER: Server process failed to terminate\n'
         debug_stream.write(msg)
         sub.kill()
         sub.wait()
         msg = b'SIGPIPE-HELPER: Server process killed\n'
     else:
         msg = b'SIGPIPE-HELPER: Server process terminated with status %d\n'
         msg %= sub.returncode
         debug_stream.write(msg)
     debug_stream.write(b'SIGPIPE-HELPER: Shut down\n')