You could try this in the local BUILD file:

python_requirements()

python_requirement_library(
  name='pyarrow',
  requirements=[
    python_requirement("pyarrow==0.9.0 ; sys_platform == 'darwin'"),
    python_requirement("pyarrow==0.9.0.post1 ; sys_platform == 'linux2'"),
  ]
)

Behind the scenes

requirements.txt

is automatically transformed into a list of single-

python_requirement

python_requirement_library

entries by

python_requirements

and it picks the name for each entry based on the requirement key - leading to dup.