Make `rpc_modules` a positional arg to `tractor.run_daemon()`

tests/test_multi_program.py

@@ -24,7 +24,7 @@ def sig_prog(proc, sig):
 def daemon(loglevel, testdir, arb_addr):
     cmdargs = [
         sys.executable, '-c',
-        "import tractor; tractor.run_daemon(arbiter_addr={}, loglevel={})"
+        "import tractor; tractor.run_daemon((), arbiter_addr={}, loglevel={})"
         .format(
             arb_addr,
             "'{}'".format(loglevel) if loglevel else None)

tractor/__init__.py

@@ -97,12 +97,14 @@ def run(
 
 
 def run_daemon(
-    rpc_modules: Optional[Tuple[str]] = None,
+    rpc_modules: Tuple[str],
     **kwargs
 ) -> None:
-    for path in rpc_modules or ():
-        importlib.import_module(path)
-
+    """Spawn a single daemon-actor which will repond to RPC.
+    """
     kwargs['rpc_module_paths'] = rpc_modules
 
+    for path in rpc_modules:
+        importlib.import_module(path)
+
     return run(partial(trio.sleep, float('inf')), **kwargs)