Many projects on github have numerical tags that represent a release version. The most obvious way to pull a specific revision of something is to use something like 'source-tag: 2.14'. However, this fails with the message: 'Can't convert 'float' object to str implicitly' The same snapcraft configuration file works as expected if the tag is enclosed in quotes, but it would be nice to not require the user to put quotes around the tag. It should work perfectly fine to add a call to str() in snapcraft.internal.sources.Base.__init__ Also, if this is something that won't be fixed, then either the error should be caught and a more helpful error message should be displayed, or a stacktrace should be displayed to make it easier to track the issue down. There is an example snapcraft configuration file attached that demonstrates the bug.