Due to a recent update, svglib version 1.6.0, a dependency of easy-thumbnails[svg], now requires pycairo. This addition causes installation to fail unless the system has system-level libraries like cario. Since the svglib maintainer has acknowledged the issue and plans to fix it, the best temporary solution is to pin svglib to version 1.5.1 in your project's dependency file to prevent this new, problematic version from being installed.

reported issue in the svglib repository:
deeplook/svglib#421