More fixes

.travis.yml

@@ -14,6 +14,6 @@ install:
   - pip install -e .
 # command to run tests
 script:
-  - isort --skip-glob=venv
+  - isort -c --skip-glob=venv
   - flake8 tests/ validate_email/
   - python -m unittest discover -v

validate_email/mx_check.py

@@ -1,33 +1,35 @@
-import re
-import smtplib
-import socket
+from re import compile as re_compile
+from smtplib import SMTP
+from socket import gethostname
 
 import dns.resolver as dns
 
+DOMAIN_REGEX = re_compile(r'(?<=@)\[?([^\[\]]+)')
+
 
 def _get_domain_from_email_address(email_address):
     try:
-        return re.search(r"(?<=@)\[?([^\[\]]+)", email_address)[1]
+        return DOMAIN_REGEX.search(string=email_address)[1]
     except TypeError:
-        raise ValueError("Invalid email address")
+        raise ValueError('Invalid email address')
     except IndexError:
-        raise ValueError("Invalid email address")
+        raise ValueError('Invalid email address')
 
 
 def _get_mx_records(domain):
     try:
         records = dns.query(domain, 'MX')
     except dns.NXDOMAIN:
-        raise ValueError("Domain {} does not seem to exist")
+        raise ValueError('Domain {} does not seem to exist')
     except Exception:
-        raise NotImplementedError("Feature not yet implemented")
+        raise NotImplementedError('Feature not yet implemented')
     return [str(x.exchange) for x in records]
 
 
 def mx_check(email_address, smtp_timeout=10):
-    host = socket.gethostname()
+    host = gethostname()
 
-    smtp = smtplib.SMTP(timeout=smtp_timeout)
+    smtp = SMTP(timeout=smtp_timeout)
     smtp.set_debuglevel(0)
 
     domain = _get_domain_from_email_address(email_address)