更新conda会导致降级和取代软件包

Question

每次我想执行conda update conda以下操作：

The following packages will be UPDATED:

  cryptography                         2.4.2-py27hc64555f_0 --> 2.6.1-py27hcfb25f9_0
  openssl                                 1.0.2r-h0c8e037_0 --> 1.1.1b-h0c8e037_1

The following packages will be SUPERSEDED by a higher-priority channel:

  jpeg                        pkgs/main::jpeg-9b-ha175dff_2 --> pkgs/free::jpeg-8d-vc9_2
  libtiff              pkgs/main::libtiff-4.0.10-h1c3b264_2 --> pkgs/free::libtiff-4.0.6-vc9_2
  pyqt                 pkgs/main::pyqt-5.6.0-py27h6e61f57_6 --> pkgs/free::pyqt-4.10.4-py27_1
  qt                     pkgs/main::qt-5.6.2-vc9hc26998b_12 --> pkgs/free::qt-4.8.7-vc9_6

The following packages will be DOWNGRADED:

  spyder                                       3.3.4-py27_0 --> 3.2.8-py27_0

完成更新后，我可以运行conda update --all，再次更新已被取代并因此降级的版本。我能以某种方式规避该问题并直接执行a conda update conda，而不必再执行更新操作，而将更新版本留给我conda update --all吗？

编辑：

输出conda config --show default_channels：

default_channels:
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/free
  - https://repo.anaconda.com/pkgs/r
  - https://repo.anaconda.com/pkgs/msys2

输出conda config --show custom_multichannels：

custom_multichannels:
  local:
  defaults:
    - https://repo.anaconda.com/pkgs/main
    - https://repo.anaconda.com/pkgs/free
    - https://repo.anaconda.com/pkgs/r
    - https://repo.anaconda.com/pkgs/msys2