WindowsError: [Error 32] The process cannot access the file because it is being used by another process: when using shutil

Question

I created some files by reading and modifying some original source files. I then copy the newly created files to the old filename using shutil. When I try to delete the files created by editing the original source, i get this error:

WindowsError: [Error 32] The process cannot access the file because it is being used by another process:

I have tried opening and closing the file and pickle

for fileB in newFilesList:
    #print "FileB: %s" % fileB
    if re.search('newfile',fileB,flags=0):
        newFileCounter+=1
        fileToGo=countFiles-newFileCounter
        print("There are %s files left to copy." % fileToGo)
        #print "we have a match!!!!!!!!!!!!!"
        os.chdir(path)
        LocPreNewfile=fileB.find('newfile')
        FileCBase=fileB[0:LocPreNewfile-1]
        FileC= FileCBase + ".shp.iso.xml"
        #print "FileCBase %s" % FileCBase
        #print "FileC: %s " % FileC
        os.chdir(path)
        if os.path.exists(fileB):
            #print "fileB %s exists!!!!!!!!!!!!!!!!!!!!!" % fileB
            if os.path.exists(FileC):
                #print "%s exists!!!!!!!!!!!!!!!!!!!!!" % FileC
                shutil.copyfile(fileB, FileC)
                if countFiles > 1:
                    if fileToGo >0:
                        os.remove(fileB)
                    else:
                        #fileD =fileB
                        print('One file left to remove: %s' % fileB)


            else:
                print ("FileC ( %s ) does not exist" % FileC)
        else:
            print ("%s does not exist" % fileB)
    #print"---------------------------------------------------\n\n"
    #print("---------------------------------------------------\n\n")
    print("---------------------------------------------------\n\n")

if os.path.exists(fileB):
   print("Removing %s" % fileB)

   os.remove(fileB)