This line warns the user that dependent environment doesn’t exist, and presents the command line
for creating an environment.
When the variable `envNamespace` is specified, the `envns` option should be available as well.
* Python Environment: add gevent based WSGI server framework
This supply gevent based WSGI server framework to Python Environment, to
allow customer to run their functions under multi-threads.
* classify the flask based application
This set up the flask based application as individual class, to make
sure the consistent and integrity.
* Add instruction of WSGI server selection applied in Python Environment
* Python Environment starting logger: provide framework name
This use constant to instead hard code for ArchiveLiteralSizeLimit. That ensure if the limitation
value is changed in cli, the controller server can follow it. Otherwise, the condition will return
error, and make error HTTP response.
Later, we should delete it in fission-cli, and make it configurable it chart, to work in fission-
servers only.
The cli spec dir flag name should be `specdir`, not `specs`, that should match to:
```go
specDirFlag := cli.StringFlag{Name: "specdir", Usage: "Directory to store specs, defaults to ./specs"}
```
in fission/main.go
Currently it cause the specific specs dir not to work.
```
$ fission spec apply --specdir <my spec dir>
Everything up to date.
```
