Ensure tests independent of ZMQ don't load it

* test/jupyter-server-test.el (jupyter-server): Replace test with one that
takes into account a `jupyter-server`s changed implementation.  Before, in
addition to talking to a kernel via the REST API, it managed a set of websocket
connections in a separate process.  Now, those websocket connections live in
the current Emacs process.

Ensure that `jupyter-test-with-notebook` uses a `jupyter-server` object by
let binding `jupyter-server-use-zmq` around its call.

(jupyter-server-ioloop-comm): New test with the same body as `jupyter-server`
had before this commit.  Skip the test unless `jupyter-server-use-zmq` is
non-nil.  Rename `jupyter-server-kernel-comm` to
`jupyter-server-ioloop-kernel-comm`.

Author: nnicandro

test/jupyter-server-test.el

@@ -257,9 +257,29 @@
 
 ;;; Server
 
-;; And `jupyter-server-kernel-comm'
 (ert-deftest jupyter-server ()
   :tags '(server)
+  (let ((jupyter-server-use-zmq nil))
+    (jupyter-test-with-notebook server
+      (jupyter-test-with-server-kernel server "python" kernel
+        (ert-info ("`jupyter-comm-layer' methods")
+          (let ((kcomm (jupyter-server-kernel-comm :kernel kernel)))
+            (should-not (jupyter-comm-alive-p kcomm))
+            (jupyter-comm-start kcomm)
+            (should (jupyter-comm-alive-p kcomm))
+            (jupyter-comm-stop kcomm)
+            (should-not (jupyter-comm-alive-p kcomm))))
+        (ert-info ("Sending/receiving")
+          (let ((client (jupyter-kernel-client)))
+            (oset client kcomm (jupyter-server-kernel-comm :kernel kernel))
+            (jupyter-start-channels client)
+            (should (json-plist-p (jupyter-kernel-info client)))
+            (jupyter-stop-channels client)))))))
+
+;; And `jupyter-server-ioloop-kernel-comm'
+(ert-deftest jupyter-server-ioloop-comm ()
+  :tags '(server)
+  (skip-unless jupyter-server-use-zmq)
   (jupyter-test-with-notebook server
     (ert-info ("`jupyter-comm-layer' methods")
       (when (jupyter-comm-alive-p server)
@@ -272,7 +292,7 @@
       (let ((id (oref kernel id)))
         (should (jupyter-api-get-kernel server id))
         (ert-info ("Connecting kernel comm to server")
-          (let ((kcomm (jupyter-server-kernel-comm
+          (let ((kcomm (jupyter-server-ioloop-kernel-comm
                         :kernel kernel)))
             (should-not (jupyter-server-kernel-connected-p server id))
             (jupyter-comm-add-handler server kcomm)
@@ -282,7 +302,7 @@
             (should-not (jupyter-comm-alive-p kcomm))
             (should (jupyter-comm-alive-p server))))
         (ert-info ("Connecting kernel comm starts server comm if necessary")
-          (let ((kcomm (jupyter-server-kernel-comm
+          (let ((kcomm (jupyter-server-ioloop-kernel-comm
                         :kernel kernel)))
             (jupyter-comm-stop server)
             (should-not (jupyter-comm-alive-p server))