Use openssl CLI tool instead of text manipulation.

Lib/test/certdata/make_ssl_certs.py

@@ -231,23 +231,6 @@ def write_cert_reference(path):
         print(refdata, file=f)
 
 
-def extract_cert(pem_cert, index):
-    result = []
-    active = False
-    for line in pem_cert.splitlines():
-        match = active
-        if line == '-----BEGIN CERTIFICATE-----':
-            if index == 0:
-                active = True
-                match = True
-            index -= 1
-        elif line == '-----END CERTIFICATE-----':
-            active = False
-        if match:
-            result.append(line)
-    return '\n'.join(result) + '\n'
-
-
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Make the custom certificate and private key files used by test_ssl and friends.')
     parser.add_argument('--days', default=days_default)
@@ -283,9 +266,7 @@ def extract_cert(pem_cert, index):
         f.write(key)
         f.write(cert)
 
-    cert = extract_cert(cert, 0)
-    with open('cert3.pem', 'w') as f:
-        f.write(cert)
+    check_call(['openssl', 'x509', '-outform', 'pem', '-in', 'keycert3.pem', '-out', 'cert3.pem'])
 
     cert, key = make_cert_key(cmdlineargs, 'fakehostname', sign=True)
     with open('keycert4.pem', 'w') as f: