Add help message on conda environment creation error. Closes #1526

[umesh-timalsina]

No description provided.

[brollb]

There are a couple main issues with this:

• There is no check ensuring that the creation command failed because the environment already exists. For example, if conda isn't installed, this will still suggest running the command with --force which won't help at all. We could probably either check the error message or the exit code. I am not sure that the exit code will be very precise or cross platform.
• As a minor point, it is already logged that the command failed so we can probably just remove that so we aren't repeating ourselves in the logs.
• We should not use __dirname in the logs as this will print weird paths. For example, if we install deepforge with nvm, this will print a long path like /home/brian/.nvm/versions/node/v12.14.1/bin/browserify. This is not likely the path the user used to run the command so it's a bit strange. It's easier just to avoid this and suggest adding the '--force' flag to overwrite any existing environment.