What do the chars %7D mean in an url query?

Question

If I access my webapp with the url

/vi/5907399890173952.html

then it works but when I look in the log files then googlebot is trying to access a similar url which generates an exception:

/vi/5907399890173952.html%7D%7D

what does it mean and how can it be handled as an exception? The message from python is:

 /vi/5251302833520640.html%7D%7D 404 20ms 0kb Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html) module=default version=release140319
66.249.67.109 - - [19/Mar/2014:07:53:32 -0700] "GET /vi/5251302833520640.html%7D%7D HTTP/1.1" 404 84 - "Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)" ms=21 cpu_ms=0 cpm_usd=0.000009 app_engine_release=1.9.1 instance=00c61b117c0bc0f980f2a37a6ac534786055d3ab
E 2014-03-19 15:53:32.678
get() takes exactly 3 arguments (2 given)

The regex that I use for the url is

('/vi/(\d+)(\.html?)?', NewHandler)

Update 140319 21:54 CET

I think I've found the leakage from a jinja2 template:

{{scored_document.fields.0.value|safe}

I patched it with another } now.

Solution

%7D is the ASCII code for the } character, which is probably leaking through from a template...

Comments

[Raja Khoury]

Twig was freaking me!

[Wamadahama]

i was freaked by blade!

[Alex Alexeev]

I've just forgot to remove a } from a variable reference in js template literal

[Viacheslav Dobromyslov]

TypeScript templates with IDE autocomplete spare my brains.

[SagaRock101]

wasted 1 hour checking on this