conda_install should check for conflicts?

I ran conda_install for a tool XML with these requirements:
```
bioconductor-customprodb
bioconductor-rgalaxy
bioconductor-biocinstaller
```

When I tried to source the result (current directory has the tool XML):
`. <(planemo conda_env .)`

I get this lovely error:
```
UnsatisfiableError: The following specifications were found to be in conflict:
- bioconductor-annotationdbi 1.36.2 r3.3.1_0
- r 3.3.2 r3.3.2_0
```

If I downgrade to:
```
bioconductor-biocinstaller
```
Then it works fine. Is there a way to pass all the conda packages to conda and once so that it finds the conflict at install time instead of when sourcing the env? And hopefully even provide a better error message.