Catch and print errors in API response

Related to #1

cli/api.py

@@ -2,8 +2,6 @@
 API utilities
 """
 
-from requests import HTTPError
-
 from strava.api._helpers import client, url, json
 
 
@@ -11,7 +9,10 @@ def post_activity(xargs):
     """API call to create an activity"""
 
     response = client.post(url=url("/activities"), data=xargs)
-    try:
-        return json(response)
-    except HTTPError:
-        return response
+
+    if response.ok:
+        result = json(response)
+    else:
+        result = response.json()
+
+    return result