Explicitly precompile the ANSI-colors regular expression

This may not be terribly important, as the re module caches patterns,
but it doesn’t hurt. Corresponds to
jonathaneunice/colors#2.

Author: musicinmybrain

papermill/exceptions.py

@@ -59,21 +59,24 @@ class PapermillParameterOverwriteWarning(PapermillWarning):
     """Callee overwrites caller argument to pass down the stream."""
 
 
+# The regular expression is copied from:
+# https://github.com/jonathaneunice/colors/blob/
+#    c965f5b9103c5bd32a1572adb8024ebe83278fb0/colors/colors.py#L122-L131
+#
+# The original docstring notes that this does not strip all possible ANSI
+# escape sequences related to color and style, but it attempts to cover the
+# most common ones and a few known oddities produced by actual colorization
+# libraries, including \x1b[K (EL, erase to end of line) and \x1b[m (more
+# commonly expressed as \x1b[0m).
+_COLORS = re.compile("\x1b\\[(K|.*?m)")
+
+
 def strip_color(text):
     """Remove most ANSI color and style sequences from a string
 
     Based on https://pypi.org/project/ansicolors/."""
 
-    # The regular expression is copied from:
-    # https://github.com/jonathaneunice/colors/blob/
-    #    c965f5b9103c5bd32a1572adb8024ebe83278fb0/colors/colors.py#L122-L131
-    #
-    # The original docstring notes that this does not strip all possible ANSI
-    # escape sequences related to color and style, but it attempts to cover the
-    # most common ones and a few known oddities produced by actual
-    # colorization libraries, including \x1b[K (EL, erase to end of line) and
-    # \x1b[m (more commonly expressed as \x1b[0m).
-    return re.sub("\x1b\\[(K|.*?m)", "", text)
+    return _COLORS.sub("", text)
 
 
 def missing_dependency_generator(package, dep):