Pandas 0.24 - cannot install with python 3.6.8
New release of pandas cannot be installed via conda. It results in error:

```
UnsatisfiableError: The following specifications were found to be in conflict:
  - pandas==0.24.0 -> python[version='>=2.7,<2.8.0a0'] -> openssl=1.0
  - pandas==0.24.0 -> python[version='>=2.7,<2.8.0a0'] -> readline=6.2
  - pandas==0.24.0 -> python[version='>=2.7,<2.8.0a0'] -> sqlite=3.13
  - pandas==0.24.0 -> python[version='>=2.7,<2.8.0a0'] -> tk=8.5
  - python==3.6.8
```