simplify/correct test logic

before this, tests were being skipped on Ubuntu 20.04 with Anaconda Python
Now, all 5 tests success

test cases/python/2 extmodule/meson.build

@@ -7,26 +7,29 @@ if meson.backend() != 'ninja'
   error('MESON_SKIP_TEST: Ninja backend required')
 endif
 
+
 py_mod = import('python')
 py = py_mod.find_installation()
-py_dep = py.dependency()
+py_dep = py.dependency(required: false)
 
-if py_dep.found()
-  subdir('ext')
+if not py_dep.found()
+  error('MESON_SKIP_TEST: Python libraries not found.')
+endif
 
-  test('extmod',
-    py,
-    args : files('blaster.py'),
-    env : ['PYTHONPATH=' + pypathdir])
+subdir('ext')
 
-  # Check we can apply a version constraint
-  dependency('python3', version: '>=@0@'.format(py_dep.version()))
+test('extmod',
+  py,
+  args : files('blaster.py'),
+  env : ['PYTHONPATH=' + pypathdir])
 
-else
-  error('MESON_SKIP_TEST: Python3 libraries not found, skipping test.')
-endif
 
 py3_pkg_dep = dependency('python3', method: 'pkg-config', required : false)
 if py3_pkg_dep.found()
   python_lib_dir = py3_pkg_dep.get_pkgconfig_variable('libdir')
+
+  # Check we can apply a version constraint
+  dependency('python3', version: '>=@0@'.format(py_dep.version()))
+else
+  message('Skipped python3 pkg-config test')
 endif

test cases/python/3 cython/meson.build

@@ -10,14 +10,13 @@ if not cython.found()
   error('MESON_SKIP_TEST: Cython3 not found.')
 endif
 
-py3_dep = dependency('python3', required : false)
+py_mod = import('python')
+py3 = py_mod.find_installation()
+py3_dep = py3.dependency(required: false)
 if not py3_dep.found()
   error('MESON_SKIP_TEST: Python library not found.')
 endif
 
-py_mod = import('python')
-py3 = py_mod.find_installation()
-py3_dep = py3.dependency()
 subdir('libdir')
 
 test('cython tester',

test cases/python/4 custom target depends extmodule/meson.build

@@ -12,6 +12,10 @@ py3 = py_mod.find_installation()
 py3_dep = py3.dependency(required : false)
 cc = meson.get_compiler('c')
 
+if not py3_dep.found()
+  error('MESON_SKIP_TEST: Python3 libraries not found, skipping test.')
+endif
+
 # Copy to the builddir so that blaster.py can find the built tachyon module
 # FIXME: We should automatically detect this case and append the correct paths
 # to PYTHONLIBDIR
@@ -24,21 +28,18 @@ import os, sys
 with open(sys.argv[1], 'rb') as f:
   assert(f.read() == b'success')
 '''
-if py3_dep.found()
-  message('Detected Python version: ' + py3_dep.version())
-  if py3_dep.version().version_compare('>=3.8') and cc.get_id() == 'msvc' and cc.version().version_compare('<=19.00.24215.1')
-    error('MESON_SKIP_TEST: Python modules do not work with Python 3.8 and VS2015 or earlier.')
-  endif
-  subdir('ext')
-
-  out_txt = custom_target('tachyon flux',
-    input : blaster_py,
-    output : 'out.txt',
-    command : [py3, '@INPUT@', '-o', '@OUTPUT@'],
-    depends : pylib,
-    build_by_default: true)
-
-  test('flux', py3, args : ['-c', check_exists, out_txt])
-else
-  error('MESON_SKIP_TEST: Python3 libraries not found, skipping test.')
+
+message('Detected Python version: ' + py3_dep.version())
+if py3_dep.version().version_compare('>=3.8') and cc.get_id() == 'msvc' and cc.version().version_compare('<=19.00.24215.1')
+  error('MESON_SKIP_TEST: Python modules do not work with Python 3.8 and VS2015 or earlier.')
 endif
+subdir('ext')
+
+out_txt = custom_target('tachyon flux',
+  input : blaster_py,
+  output : 'out.txt',
+  command : [py3, '@INPUT@', '-o', '@OUTPUT@'],
+  depends : pylib,
+  build_by_default: true)
+
+test('flux', py3, args : ['-c', check_exists, out_txt])