Fix #438 util and pkio were circular imports (#439)

pykern/pkio.py

@@ -4,7 +4,7 @@
 :license: http://www.apache.org/licenses/LICENSE-2.0.html
 """
 
-# Root module: Limit imports to  avoid dependency issues
+# Root module: Limit imports to avoid dependency issues
 from pykern import pkconst
 from pykern import pkinspect
 import contextlib
@@ -15,7 +15,6 @@
 import os
 import os.path
 import py
-import pykern.util
 import random
 import re
 import shutil
@@ -139,9 +138,11 @@ def is_pure_text(filepath, test_size=512):
     Returns:
         bool: True if file is likely pure text, false if likely binary
     """
+    from pykern import util
+
     with open(filepath, "rb") as f:
         b = f.read(test_size + 1)
-    return pykern.util.is_pure_text(b[:test_size], is_truncated=len(b) > test_size)
+    return util.is_pure_text(b[:test_size], is_truncated=len(b) > test_size)
 
 
 def mkdir_parent(path):

pykern/util.py

@@ -3,10 +3,7 @@
 :copyright: Copyright (c) 2023 RadiaSoft LLC.  All Rights Reserved.
 :license: http://www.apache.org/licenses/LICENSE-2.0.html
 """
-from pykern import pkconfig
-from pykern import pkinspect
-from pykern import pkio
-from pykern.pkdebug import pkdc, pkdexc, pkdlog, pkdp
+# Root module: Limit imports to avoid dependency issues
 import os.path
 import sys
 
@@ -26,6 +23,8 @@ def cfg_absolute_dir(value):
     Returns:
         py.path.Local absolute path to dir
     """
+    from pykern import pkio, pkconfig
+
     if not os.path.isabs(value):
         pkconfig.raise_error("must be absolute")
     if not os.path.isdir(value):
@@ -48,6 +47,7 @@ def dev_run_dir(package_object):
     Raises:
         AssertionError: Raised when not in development mode
     """
+    from pykern import pkio, pkconfig, pkinspect
 
     def _check_dev_files(root):
         """Check for files that only exist in development"""