Move reproject imports to function level

reproject is not available on some old Linux distributions that
we have to support still.
11 jobs for wcsaxes-reproject in 41 minutes and 5 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Nightly
passed nightly:macos #35598
macos

00:41:05

passed nightly:mpi:jessie #35595

00:37:09

passed nightly:openmp:jessie #35596

00:37:13

passed nightly:python3:stretch #35597

00:38:17

failed nightly:top-level:artful #35592
allowed to fail

00:22:40

failed nightly:top-level:buster #35593
allowed to fail

00:24:54

passed nightly:top-level:clang #35594

00:37:28

passed nightly:top-level:el7 #35588

00:35:21

passed nightly:top-level:stretch #35589

00:38:07

passed nightly:top-level:trusty #35590

00:28:47

passed nightly:top-level:xenial #35591

00:30:58

 
Name Stage Failure
failed
nightly:top-level:buster Nightly
Makefile:403: recipe for target 'check-recursive' failed
make[2]: *** [check-recursive] Error 1
make[2]: Leaving directory '/builds/leo-singer/lalsuite/lalsuite-6.48.1/_build/sub'
make[1]: *** [check] Error 2
Makefile:677: recipe for target 'check' failed
make[1]: Leaving directory '/builds/leo-singer/lalsuite/lalsuite-6.48.1/_build/sub'
Makefile:594: recipe for target 'distcheck' failed
make: *** [distcheck] Error 1
ERROR: Job failed: exit code 1
failed
nightly:top-level:artful Nightly
make[2]: *** [check-recursive] Error 1
Makefile:403: recipe for target 'check-recursive' failed
make[2]: Leaving directory '/builds/leo-singer/lalsuite/lalsuite-6.48.1/_build/sub'
Makefile:677: recipe for target 'check' failed
make[1]: *** [check] Error 2
make[1]: Leaving directory '/builds/leo-singer/lalsuite/lalsuite-6.48.1/_build/sub'
Makefile:594: recipe for target 'distcheck' failed
make: *** [distcheck] Error 1
ERROR: Job failed: exit code 1