Run oscrypto_check_hostname in a ThreadPoolExecutor

because oscrpyto doesn't provide async APIs. See:
wbond/oscrypto#1

The two solutions to the blocking problem is:
- completely remove oscrypto support and only call Python's build in
  non-blocking APIs
- run oscrypto calls in a ThreadPoolExecutor

certmaestro/check.py

@@ -56,14 +56,18 @@ def oscrypto_check_hostname(hostname):
 
 
 class CheckSiteManager:
-    def __init__(self, redirect, timeout, retries):
+    def __init__(self, redirect, timeout, retries, *, loop=None):
         self.redirect = redirect
         self.timeout = timeout
         self.retries = retries
         self.skipped = []
         self.succeeded = []
         self.failed = []
 
+        executor = futures.ThreadPoolExecutor(max_workers=10)
+        self.loop = loop or asyncio.get_event_loop()
+        self.loop.set_default_executor(executor)
+
     @property
     def success_count(self):
         return len(self.succeeded)
@@ -124,7 +128,7 @@ async def _check_hostname(self, hostname):
             return CheckedSite(hostname, CheckResult.FAILED, openssl_error)
         else:
             # OSCrypto gives better error messages, but it is less strict
-            oscrypto_error = oscrypto_check_hostname(hostname)
+            oscrypto_error = await self.loop.run_in_executor(None, oscrypto_check_hostname, hostname)
             error_message = oscrypto_error or openssl_error
             return CheckedSite(hostname, CheckResult.FAILED, error_message)
 

certmaestro/cli/groups/site.py

@@ -58,8 +58,8 @@ def check(ctx, urls, timeout, retries, redirect):
 
     click.echo('Checking certificates...')
 
-    manager = CheckSiteManager(redirect, timeout, retries)
     loop = asyncio.get_event_loop()
+    manager = CheckSiteManager(redirect, timeout, retries, loop=loop)
     loop.run_until_complete(_check_sites(manager, urls))
 
     total_message = click.style(f'Total: {len(urls)}', fg='blue')