Use normal deprecation warning

skimage/_shared/utils.py

@@ -19,16 +19,6 @@ class skimage_deprecation(Warning):
     pass
 
 
-def deprecation_warning(msg, **kwargs):
-    """Emit deprecation warning for scikit-image.
-
-    Unlike default deprecation warnings, this is not silenced by default.
-    Additional keyword arguments are passed to `warnings.warn`.
-    """
-    warnings.simplefilter('always', skimage_deprecation)
-    warnings.warn(msg, category=skimage_deprecation, **kwargs)
-
-
 class deprecated(object):
     """Decorator to mark deprecated functions with warning.
 

skimage/exposure/exposure.py

@@ -3,7 +3,6 @@ import numpy as np
 
 from skimage import img_as_float
 from skimage.util.dtype import dtype_range, dtype_limits
-from skimage._shared.utils import deprecation_warning
 
 
 __all__ = ['histogram', 'cumulative_distribution', 'equalize',
@@ -255,12 +254,12 @@ def rescale_intensity(image, in_range='image', out_range='dtype'):
     if in_range is None:
         in_range = 'image'
         msg = "`in_range` should not be set to None. Use {!r} instead."
-        deprecation_warning(msg.format(in_range))
+        warnings.warn(msg.format(in_range))
 
     if out_range is None:
         out_range = 'dtype'
         msg = "`out_range` should not be set to None. Use {!r} instead."
-        deprecation_warning(msg.format(out_range))
+        warnings.warn(msg.format(out_range))
 
     imin, imax = intensity_range(image, in_range)
     omin, omax = intensity_range(image, out_range, clip_negative=(imin >= 0))