diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index c6f6f61..3fc499e 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -268,6 +268,41 @@
         finally:
             self.unfakehttp()
 
+    def test_missing_localfile(self):
+        # Test for #10836
+        with self.assertRaises(urllib.error.URLError) as e:
+            urlopen('file://localhost/a/file/which/doesnot/exists.py')
+        self.assertTrue(e.exception.filename)
+        self.assertTrue(e.exception.reason)
+
+    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))
+        with self.assertRaises(urllib.error.URLError):
+            urlopen(tmp_fileurl)
+
+    def test_ftp_nohost(self):
+        test_ftp_url = 'ftp:///path'
+        with self.assertRaises(urllib.error.URLError) as e:
+            urlopen(test_ftp_url)
+        self.assertFalse(e.exception.filename)
+        self.assertTrue(e.exception.reason)
+
+    def test_ftp_nonexisting(self):
+        with self.assertRaises(urllib.error.URLError) as e:
+            urlopen('ftp://localhost/a/file/which/doesnot/exists.py')
+        self.assertFalse(e.exception.filename)
+        self.assertTrue(e.exception.reason)
+
+
     def test_userpass_inurl(self):
         self.fakehttp(b"HTTP/1.0 200 OK\r\n\r\nHello!")
         try:
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index 64092cf..eb45c7e 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1300,9 +1300,9 @@
                 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):
@@ -1361,8 +1361,8 @@
                 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):
@@ -1662,7 +1662,6 @@
                 if proxy_bypass(realhost):
                     host = realhost
 
-            #print "proxy via http:", host, selector
         if not host: raise IOError('http error', 'no host given')
 
         if proxy_passwd:
@@ -1753,7 +1752,7 @@
     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:
@@ -1768,7 +1767,7 @@
         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]
@@ -1782,23 +1781,22 @@
             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
-        from io import StringIO
         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)
@@ -1847,13 +1845,13 @@
                 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:
@@ -2184,7 +2182,7 @@
                 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!
@@ -2196,7 +2194,7 @@
                     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
@@ -2464,7 +2462,6 @@
             test = test.replace("*", r".*")     # change glob sequence
             test = test.replace("?", r".")      # change glob char
             for val in host:
-                # print "%s <--> %s" %( test, val )
                 if re.match(test, val, re.I):
                     return 1
         return 0
diff --git a/Misc/NEWS b/Misc/NEWS
index e6948d7..a7af2cc 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -132,6 +132,8 @@
 Library
 -------
 
+- Issue #16250: Fix URLError invocation with proper args.
+
 - Issue #16305: Fix a segmentation fault occurring when interrupting
   math.factorial.