diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 22ada56..623eb5e 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -268,6 +268,39 @@
         finally:
             self.unfakehttp()
 
+    def test_missing_localfile(self):
+        # Test for #10836
+        # 3.3 - URLError is not captured, explicit IOError is raised.
+        with self.assertRaises(IOError):
+            urlopen('file://localhost/a/file/which/doesnot/exists.py')
+
+    def test_file_notexists(self):
+        fd, tmp_file = tempfile.mkstemp()
+        tmp_fileurl = 'file://localhost/' + tmp_file.replace(os.path.sep, '/')
+        try:
+            self.assertTrue(os.path.exists(tmp_file))
+            with urlopen(tmp_fileurl) as fobj:
+                self.assertTrue(fobj)
+        finally:
+            os.close(fd)
+            os.unlink(tmp_file)
+        self.assertFalse(os.path.exists(tmp_file))
+        # 3.3 - IOError instead of URLError
+        with self.assertRaises(IOError):
+            urlopen(tmp_fileurl)
+
+    def test_ftp_nohost(self):
+        test_ftp_url = 'ftp:///path'
+        # 3.3 - IOError instead of URLError
+        with self.assertRaises(IOError):
+            urlopen(test_ftp_url)
+
+    def test_ftp_nonexisting(self):
+        # 3.3 - IOError instead of URLError
+        with self.assertRaises(IOError):
+            urlopen('ftp://localhost/a/file/which/doesnot/exists.py')
+
+
     def test_userpass_inurl(self):
         self.fakehttp(b"HTTP/1.0 200 OK\r\n\r\nHello!")
         try:
@@ -300,7 +333,7 @@
 
     def test_URLopener_deprecation(self):
         with support.check_warnings(('',DeprecationWarning)):
-            warn = urllib.request.URLopener()
+            urllib.request.URLopener()
 
 class urlretrieve_FileTests(unittest.TestCase):
     """Test urllib.urlretrieve() on local files"""
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 88f3ce1..27ab2b9 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1413,9 +1413,9 @@
                 else:
                     origurl = 'file://' + filename
                 return addinfourl(open(localfile, 'rb'), headers, origurl)
-        except OSError as msg:
+        except OSError as exp:
             # users shouldn't expect OSErrors coming from urlopen()
-            raise URLError(msg)
+            raise URLError(exp)
         raise URLError('file not on local host')
 
 def _safe_gethostbyname(host):
@@ -1474,8 +1474,8 @@
                 headers += "Content-length: %d\n" % retrlen
             headers = email.message_from_string(headers)
             return addinfourl(fp, headers, req.full_url)
-        except ftplib.all_errors as msg:
-            exc = URLError('ftp error: %s' % msg)
+        except ftplib.all_errors as exp:
+            exc = URLError('ftp error: %r' % exp)
             raise exc.with_traceback(sys.exc_info()[2])
 
     def connect_ftp(self, user, passwd, host, port, dirs, timeout):
@@ -1870,7 +1870,7 @@
     def open_file(self, url):
         """Use local file or FTP depending on form of URL."""
         if not isinstance(url, str):
-            raise URLError('file error', 'proxy support for file protocol currently not implemented')
+            raise URLError('file error: proxy support for file protocol currently not implemented')
         if url[:2] == '//' and url[2:3] != '/' and url[2:12].lower() != 'localhost/':
             raise ValueError("file:// scheme is supported only on localhost")
         else:
@@ -1885,7 +1885,7 @@
         try:
             stats = os.stat(localname)
         except OSError as e:
-            raise URLError(e.errno, e.strerror, e.filename)
+            raise URLError(e.strerror, e.filename)
         size = stats.st_size
         modified = email.utils.formatdate(stats.st_mtime, usegmt=True)
         mtype = mimetypes.guess_type(url)[0]
@@ -1899,22 +1899,22 @@
             return addinfourl(open(localname, 'rb'), headers, urlfile)
         host, port = splitport(host)
         if (not port
-           and socket.gethostbyname(host) in (localhost() + thishost())):
+           and socket.gethostbyname(host) in ((localhost(),) + thishost())):
             urlfile = file
             if file[:1] == '/':
                 urlfile = 'file://' + file
             elif file[:2] == './':
                 raise ValueError("local file url may start with / or file:. Unknown url of type: %s" % url)
             return addinfourl(open(localname, 'rb'), headers, urlfile)
-        raise URLError('local file error', 'not on local host')
+        raise URLError('local file error: not on local host')
 
     def open_ftp(self, url):
         """Use FTP protocol."""
         if not isinstance(url, str):
-            raise URLError('ftp error', 'proxy support for ftp protocol currently not implemented')
+            raise URLError('ftp error: proxy support for ftp protocol currently not implemented')
         import mimetypes
         host, path = splithost(url)
-        if not host: raise URLError('ftp error', 'no host given')
+        if not host: raise URLError('ftp error: no host given')
         host, port = splitport(host)
         user, host = splituser(host)
         if user: user, passwd = splitpasswd(user)
@@ -1963,13 +1963,13 @@
                 headers += "Content-Length: %d\n" % retrlen
             headers = email.message_from_string(headers)
             return addinfourl(fp, headers, "ftp:" + url)
-        except ftperrors() as msg:
-            raise URLError('ftp error', msg).with_traceback(sys.exc_info()[2])
+        except ftperrors() as exp:
+            raise URLError('ftp error %r' % exp).with_traceback(sys.exc_info()[2])
 
     def open_data(self, url, data=None):
         """Use "data" URL."""
         if not isinstance(url, str):
-            raise URLError('data error', 'proxy support for data protocol currently not implemented')
+            raise URLError('data error: proxy support for data protocol currently not implemented')
         # ignore POSTed data
         #
         # syntax of data URLs:
@@ -2298,7 +2298,7 @@
                 conn, retrlen = self.ftp.ntransfercmd(cmd)
             except ftplib.error_perm as reason:
                 if str(reason)[:3] != '550':
-                    raise URLError('ftp error', reason).with_traceback(
+                    raise URLError('ftp error: %d' % reason).with_traceback(
                         sys.exc_info()[2])
         if not conn:
             # Set transfer mode to ASCII!
@@ -2310,7 +2310,7 @@
                     try:
                         self.ftp.cwd(file)
                     except ftplib.error_perm as reason:
-                        raise URLError('ftp error', reason) from reason
+                        raise URLError('ftp error: %d' % reason) from reason
                 finally:
                     self.ftp.cwd(pwd)
                 cmd = 'LIST ' + file
diff --git a/Misc/NEWS b/Misc/NEWS
index da227f7..e0a54cb 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -49,6 +49,8 @@
 Library
 -------
 
+- Issue #16250: Fix URLError invocation with proper args.
+
 - Issue #16116: Fix include and library paths to be correct when building C
   extensions in venvs.