Run submission in a separate thread, and more explicit state

Also more explicit timeouts and an overall better handling of errors.

benchmark/submission/exceptions.py

@@ -0,0 +1,23 @@
+import requests
+
+
+class CommunicationError(requests.exceptions.BaseHTTPError):
+    """Raised when we get an invalid status code form the MyData server."""
+
+    def __init__(self, message: str, response: requests.Response):
+        self.message = message
+        self.status_code = response.status_code
+        self.body = response.text
+
+        if response.headers.get('Content-Type', '') == 'application/json':
+            self.json = response.json()
+        else:
+            self.json = None
+
+    def __str__(self):
+        return f'{self.message}; ' \
+               f'status_code={self.status_code}; json={self.json}; body={self.body}'
+
+
+class TokenTimeoutError(Exception):
+    """Raised when there was a timeout waiting for a client token."""