It doesn't generate anything and prints some strange messages

I run codegen like this:

$ docker run -it swaggerapi/swagger-codegen-cli generate -i aaa.json -l html

And it prints some odd things:

[main] INFO io.swagger.parser.Swagger20Parser - reading from aaa.json
[main] INFO io.swagger.parser.Swagger20Parser - reading from aaa.json
[main] ERROR io.swagger.parser.SwaggerCompatConverter - failed to read resource listing
java.lang.RuntimeException: Could not find aaa.json on the classpath
        at io.swagger.parser.util.ClasspathHelper.loadFileFromClasspath(ClasspathHelper.java:31)
        at io.swagger.parser.SwaggerCompatConverter.readResourceListing(SwaggerCompatConverter.java:206)
        at io.swagger.parser.SwaggerCompatConverter.read(SwaggerCompatConverter.java:122)
        at io.swagger.parser.SwaggerParser.read(SwaggerParser.java:96)
        at io.swagger.codegen.config.CodegenConfigurator.toClientOptInput(CodegenConfigurator.java:450)
        at io.swagger.codegen.cmd.Generate.run(Generate.java:305)
        at io.swagger.codegen.SwaggerCodegen.main(SwaggerCodegen.java:35)
[main] INFO io.swagger.codegen.ignore.CodegenIgnoreProcessor - No .swagger-codegen-ignore file found.
Exception in thread "main" java.lang.RuntimeException: missing swagger input or config!
        at io.swagger.codegen.DefaultGenerator.generate(DefaultGenerator.java:766)
        at io.swagger.codegen.cmd.Generate.run(Generate.java:307)
        at io.swagger.codegen.SwaggerCodegen.main(SwaggerCodegen.java:35)

And this one is especially confusing:

java.lang.RuntimeException: Could not find aaa.json on the classpath

It's just a file in the current directory, why would it want to be on the classpath?

P.S. Is my understand correct that -l html is gonna build this page?

Reproduce the docker command with the supplied aaa.json input, then trace input handling from Generate.run through CodegenConfigurator.toClientOptInput, SwaggerParser.read, and DefaultGenerator.generate. Check the existing CLI tests or documentation for local-file inputs and the html generator; done means the command's expected behavior and error message are covered.