Fix modin test (#4069)

python/setup.py

@@ -84,7 +84,13 @@ class build_ext(_build_ext.build_ext):
             for name in filenames:
                 pyarrow_files.append(os.path.join(root, name))
 
-        files_to_include = ray_files + pyarrow_files
+        # Make sure the relevant files for modin get copied.
+        modin_files = []
+        for (root, dirs, filenames) in os.walk("./ray/modin"):
+            for name in filenames:
+                modin_files.append(os.path.join(root, name))
+
+        files_to_include = ray_files + pyarrow_files + modin_files
 
         # Copy over the autogenerated flatbuffer Python bindings.
         for directory in generated_python_directories:
@@ -144,6 +150,8 @@ requires = [
     "redis",
     # The six module is required by pyarrow.
     "six >= 1.0.0",
+    # The typing module is required by modin.
+    "typing",
     "flatbuffers",
     "faulthandler;python_version<'3.3'",
 ]