Update README.md with a comment for when creation of minimal environment fails.

README.md

@@ -122,6 +122,8 @@ Some rules will use this environment.
     conda env create -f ./envs/MetaSnk.yaml
     conda activate MetaSnk
 
+If this step fails, be sure that the dependencies listed before are already installed!
+
 ##### Download singularity containers and reference databases
 MetaSnk wraps system requirements and software dependencies within singularity containers.
 Download these containers by running rule 'pullSIFS' :