Eliminate PIL warning from why.read() (#1544)

## Description

Don't warn if PIL is missing when importing `ImageMetric` for
`why.read()`.

## Changes

- Don't issue warning on import, just `ImageMetric` construction.
- Silence the warning when setting up for `why.read()`

## Related

Relates to #1490
Closes #1490

python/whylogs/extras/image_metric.py

@@ -28,17 +28,17 @@
 
 logger = logging.getLogger(__name__)
 
+
 try:
     import numpy as np  # type: ignore
     from PIL import Image
     from PIL.Image import Image as ImageType  # type: ignore
     from PIL.ImageStat import Stat  # type: ignore
     from PIL.TiffImagePlugin import IFDRational  # type: ignore
     from PIL.TiffTags import TAGS  # type: ignore
-except ImportError as e:
+except ImportError:
     ImageType = None  # type: ignore
-    logger.warning(str(e))
-    logger.warning("Unable to load PIL; install Pillow for image support")
+
 
 DEFAULT_IMAGE_FEATURES: List[str] = []
 
@@ -147,6 +147,10 @@ def resolve(self, name: str, why_type: DataType, fi_disabled: bool = False) -> D
         return metrics
 
 
+def _no_pil_msg():
+    logger.error("Unable to import PIL; install Pillow for image support")
+
+
 @dataclass(frozen=True)
 class ImageMetricConfig(MetricConfig):
     allowed_exif_tags: Set[str] = field(default_factory=set)
@@ -164,7 +168,7 @@ def __init__(
         fi_disabled: bool = False,
     ):
         if ImageType is None:
-            logger.error("Install Pillow for image support")
+            _no_pil_msg()
         super(ImageMetric, self).__init__(submetrics)
         self._allowed_exif_tags = allowed_exif_tags or set()
         self._forbidden_exif_tags = forbidden_exif_tags or set()
@@ -303,4 +307,7 @@ def resolve(self, name: str, why_type: DataType, column_schema: ColumnSchema) ->
 
 
 # Register it so Multimetric and ProfileView can deserialize
+tmp = _no_pil_msg
+_no_pil_msg = lambda: None  # noqa
 register_metric(ImageMetric)
+_no_pil_msg = tmp