Improve startuptime: don't import IPython/ipykernal if not in jupyter (…

…#1001)

Co-authored-by: Delgan <delgan.py@gmail.com>

loguru/_colorama.py

@@ -1,3 +1,4 @@
+import builtins
 import os
 import sys
 
@@ -6,7 +7,7 @@ def should_colorize(stream):
     if stream is None:
         return False
 
-    if stream is sys.stdout or stream is sys.stderr:
+    if getattr(builtins, "__IPYTHON__", False) and (stream is sys.stdout or stream is sys.stderr):
         try:
             import ipykernel
             import IPython

tests/test_colorama.py

@@ -1,3 +1,4 @@
+import builtins
 import os
 import sys
 from unittest.mock import MagicMock
@@ -172,13 +173,24 @@ class Shell:
     ipykernel.zmqshell.ZMQInteractiveShell = Shell
     ipykernel.iostream.OutStream = out_class
 
+    monkeypatch.setattr(builtins, "__IPYTHON__", True, raising=False)
     monkeypatch.setitem(sys.modules, "IPython", ipython)
     monkeypatch.setitem(sys.modules, "ipykernel", ipykernel)
     monkeypatch.setattr(sys, patched, stream, raising=False)
 
     assert should_colorize(stream) is expected
 
 
+def test_jupyter_missing_lib(monkeypatch):
+    # Missing ipykernal so jupyter block will err, should handle gracefully
+    stream = StreamIsattyFalse()
+
+    monkeypatch.setattr(builtins, "__IPYTHON__", True, raising=False)
+    monkeypatch.setattr(sys, "stdout", stream)
+
+    assert should_colorize(stream) is False
+
+
 @pytest.mark.parametrize("patched", ["__stdout__", "__stderr__"])
 @pytest.mark.skipif(os.name == "nt", reason="Colorama is required on Windows")
 def test_dont_wrap_on_linux(monkeypatch, patched, patch_colorama):