chore: try fix setting start method (#5896)

Signed-off-by: Joan Fontanals Martinez <joan.martinez@jina.ai>

jina/__init__.py

@@ -55,7 +55,15 @@ def _warning_on_one_line(message, category, filename, lineno, *args, **kwargs):
     # https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
     from multiprocessing import set_start_method as _set_start_method
 
-    _set_start_method('fork')
+    try:
+        _set_start_method('fork')
+        _warnings.warn(
+            f'multiprocessing start method is set to `fork`'
+        )
+    except Exception as e:
+        _warnings.warn(
+            f'failed to set multiprocessing start_method to `fork`: {e!r}'
+            )
 
 # do not change this line manually
 # this is managed by git tag and updated on every release

jina/helper.py

@@ -1310,25 +1310,16 @@ def run(self):
     if loop and loop.is_running():
         # eventloop already exist
         # running inside Jupyter
-        if is_jupyter():
-            thread = _RunThread()
-            thread.start()
-            thread.join()
-            try:
-                return thread.result
-            except AttributeError:
-                from jina.excepts import BadClient
-
-                raise BadClient(
-                    'something wrong when running the eventloop, result can not be retrieved'
-                )
-        else:
+        thread = _RunThread()
+        thread.start()
+        thread.join()
+        try:
+            return thread.result
+        except AttributeError:
+            from jina.excepts import BadClient
 
-            raise RuntimeError(
-                'you have an eventloop running but not using Jupyter/ipython, '
-                'this may mean you are using Jina with other integration? if so, then you '
-                'may want to use Client/Flow(asyncio=True). If not, then '
-                'please report this issue here: https://github.com/jina-ai/jina'
+            raise BadClient(
+                'something wrong when running the eventloop, result can not be retrieved'
             )
     else:
         return asyncio.run(func(*args, **kwargs))