TST: Fix test_coercion for period dtype
TST: Fix test_coercion for period dtype

xref #13941.

Author: sinhrks <sinhrks@gmail.com>

Closes #14025 from sinhrks/test_coercion_period and squashes the following commits:

b873683 [sinhrks] TST: Fix test_coercion for period dtype

cython-testbed/pandas,toobaz/pandas,gfyoung/pandas,cbertinato/pandas,cython-testbed/pandas,GuessWhoSamFoo/pandas,amolkahat/pandas,linebp/pandas,linebp/pandas,MJuddBooth/pandas,cbertinato/pandas,cython-testbed/pandas,jreback/pandas,MJuddBooth/pandas,toobaz/pandas,Winand/pandas,toobaz/pandas,toobaz/pandas,DGrady/pandas,jreback/pandas,jmmease/pandas,gfyoung/pandas,pratapvardhan/pandas,MJuddBooth/pandas,rs2/pandas,kdebrab/pandas,jorisvandenbossche/pandas,jmmease/pandas,jreback/pandas,datapythonista/pandas,harisbal/pandas,nmartensen/pandas,zfrenchee/pandas,winklerand/pandas,pratapvardhan/pandas,jmmease/pandas,TomAugspurger/pandas,winklerand/pandas,GuessWhoSamFoo/pandas,nmartensen/pandas,louispotok/pandas,nmartensen/pandas,MJuddBooth/pandas,GuessWhoSamFoo/pandas,jreback/pandas,dsm054/pandas,Winand/pandas,pratapvardhan/pandas,amolkahat/pandas,nmartensen/pandas,toobaz/pandas,DGrady/pandas,pandas-dev/pandas,dsm054/pandas,harisbal/pandas,jmmease/pandas,DGrady/pandas,linebp/pandas,harisbal/pandas,harisbal/pandas,linebp/pandas,pandas-dev/pandas,zfrenchee/pandas,louispotok/pandas,Winand/pandas,winklerand/pandas,cbertinato/pandas,pratapvardhan/pandas,kdebrab/pandas,winklerand/pandas,linebp/pandas,zfrenchee/pandas,Winand/pandas,DGrady/pandas,rs2/pandas,winklerand/pandas,cbertinato/pandas,kdebrab/pandas,dsm054/pandas,kdebrab/pandas,GuessWhoSamFoo/pandas,pratapvardhan/pandas,rs2/pandas,cython-testbed/pandas,jorisvandenbossche/pandas,datapythonista/pandas,gfyoung/pandas,Winand/pandas,jmmease/pandas,DGrady/pandas,jorisvandenbossche/pandas,gfyoung/pandas,pandas-dev/pandas,TomAugspurger/pandas,GuessWhoSamFoo/pandas,jorisvandenbossche/pandas,TomAugspurger/pandas,rs2/pandas,dsm054/pandas,amolkahat/pandas,linebp/pandas,dsm054/pandas,kdebrab/pandas,zfrenchee/pandas,cbertinato/pandas,gfyoung/pandas,TomAugspurger/pandas,zfrenchee/pandas,louispotok/pandas,louispotok/pandas,cython-testbed/pandas,MJuddBooth/pandas,pandas-dev/pandas,jmmease/pandas,Winand/pandas,jreback/pandas,datapythonista/pandas,harisbal/pandas,datapythonista/pandas,DGrady/pandas,amolkahat/pandas,nmartensen/pandas,louispotok/pandas,amolkahat/pandas,winklerand/pandas,nmartensen/pandas