[yt-dev] Issue #1264: Ambiguity when converting between code units of two datasets (yt_analysis/yt)

[Nathan Goldbaum]

New issue 1264: Ambiguity when converting between code units of two datasets
https://bitbucket.org/yt_analysis/yt/issues/1264/ambiguity-when-converting-between-code

Nathan Goldbaum:

This is illustrated by the following test script:

```
from yt.testing import fake_random_ds

ds1 = fake_random_ds(32, length_unit=1)
ds2 = fake_random_ds(32, length_unit=3)

l1 = ds1.quan(0.3, 'unitary')
l2 = ds2.quan(l1, 'unitary')

print l1.in_cgs()
print l2.in_cgs()
print ds1.quan(0.3, 'unitary').in_cgs()
print ds2.quan(0.3, 'unitary').in_cgs()
```

Right now this prints:

```
0.9 cm
0.9 cm
0.3 cm
0.9 cm
```

I would expect it to print:

```
0.3 cm
0.9 cm
0.3 cm
0.9 cm
```

I noticed @brittonsmith was working around this, but I don't think it should be necessary to do that.

Responsible: ngoldbaum