TST: packers not finding blosc/zlib should be an ImportError

Author: jreback

ci/requirements-2.7_COMPAT.pip

@@ -1,3 +1,2 @@
-blosc
 openpyxl
 argparse

pandas/io/packers.py

@@ -77,15 +77,15 @@ def _check_zlib():
         pass
 except ImportError:
     def _check_zlib():
-        raise ValueError('zlib is not installed')
+        raise ImportError('zlib is not installed')
 
 _check_zlib.__doc__ = dedent(
     """\
     Check if zlib is installed.
 
     Raises
     ------
-    ValueError
+    ImportError
         Raised when zlib is not installed.
     """,
 )
@@ -97,15 +97,15 @@ def _check_blosc():
         pass
 except ImportError:
     def _check_blosc():
-        raise ValueError('blosc is not installed')
+        raise ImportError('blosc is not installed')
 
 _check_blosc.__doc__ = dedent(
     """\
     Check if blosc is installed.
 
     Raises
     ------
-    ValueError
+    ImportError
         Raised when blosc is not installed.
     """,
 )