Retry intermittent 401 Unauthorized requests

src/apiutils.nim

@@ -61,9 +61,19 @@ template fetchImpl(result, fetchBody) {.dirty.} =
   try:
     var resp: AsyncResponse
     pool.use(genHeaders(token)):
+      template getContent =
         resp = await c.get($url)
         result = await resp.body
 
+      getContent()
+
+      # Twitter randomly returns 401 errors with an empty body quite often.
+      # Retrying the request usually works.
+      var attempt = 0
+      while resp.status == "401 Unauthorized" and result.len == 0 and attempt < 3:
+        inc attempt
+        getContent()
+
     if resp.status == $Http503:
       badClient = true
       raise newException(InternalError, result)