Python: Explicit pandas import makes it a hard requirement

[asfimport]

See https://github.com/apache/arrow/blob/master/python/pyarrow/compat.py#L24

Reporter: Uwe Korn / @xhochy
Assignee: Wes McKinney / @wesm

Related issues:

• Arrow 0.3 release (blocks)

_{Note: This issue was originally created as ARROW-715. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
I just marked this as a blocker so that pandas can be made a soft requirement.

[asfimport]

Wes McKinney / @wesm:
PR: #462

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 462
#462