Make regular expression accept a whitespace after CN.

The output of OpenSSL 1.1.0c, included in Debian Testing adds a
whitespace there. Obtaining a certificate list fails that way, since the
list of domains is empty.

acme_tiny.py

@@ -69,7 +69,7 @@ def get_crt(account_key, csr, acme_dir, log=LOGGER, CA=DEFAULT_CA):
     if proc.returncode != 0:
         raise IOError("Error loading {0}: {1}".format(csr, err))
     domains = set([])
-    common_name = re.search(r"Subject:.*? CN=([^\s,;/]+)", out.decode('utf8'))
+    common_name = re.search(r"Subject:.*? CN ?=([^\s,;/]+)", out.decode('utf8'))
     if common_name is not None:
         domains.add(common_name.group(1))
     subject_alt_names = re.search(r"X509v3 Subject Alternative Name: \n +([^\n]+)\n", out.decode('utf8'), re.MULTILINE|re.DOTALL)