Can't get Sage 7.3 to start up in Mac OS X ver. 10.12 (Sierra)

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Attempting to run Sage on a MacBook Pro running Mac OS X ver. 10.12 (Sierra). When I start up Sage I get the following messages in my terminal window:

Last login: Fri Oct 7 00:13:52 on ttys000 '/Applications/SageMath-7.3.app/Contents/Resources/sage/sage' --notebook=sagenb -bash: /Applications/mesasdk/bin/mesasdk_init.sh: No such file or directory users-MacBook-Pro:~ user$ '/Applications/SageMath-7.3.app/Contents/Resources/sage/sage' --notebook=sagenb sys:1: RuntimeWarning: not adding directory '' to sys.path since it's writable by an untrusted group. Untrusted users could put files in this directory which might then be imported by your Python code. As a general precaution from similar exploits, you should not execute Python code from this directory ┌────────────────────────────────────────────────────────────────────┐ │ SageMath version 7.3, Release Date: 2016-08-04 │ │ Type "notebook()" for the browser-based notebook interface. │ │ Type "help()" for help. │ └────────────────────────────────────────────────────────────────────┘ Please wait while the old SageNB Notebook server starts... Setting permissions of DOT_SAGE directory so only you can read and write it. Traceback (most recent call last): File "/Applications/SageMath-7.3.app/Contents/Resources/sage/src/bin/sage-notebook", line 225, in <module> launcher(unknown) File "/Applications/SageMath-7.3.app/Contents/Resources/sage/src/bin/sage-notebook", line 69, in __init__ from sagenb.notebook.notebook_object import notebook File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sagenb/notebook/notebook_object.py", line 17, in <module> import notebook as _notebook File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sagenb/notebook/notebook.py", line 35, in <module> from sagenb.misc.misc import (pad_zeros, cputime, tmp_dir, load, save, File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sagenb/misc/misc.py", line 196, in <module> import sage.all File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/all.py", line 92, in <module> from sage.misc.all import * # takes a while File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/misc/all.py", line 5, in <module> from .misc import (alarm, cancel_alarm, File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/misc/misc.py", line 143, in <module> os.chmod(DOT_SAGE, _desired_mode) OSError: [Errno 1] Operation not permitted: '/Users/user/.sage/' users-MacBook-Pro:~ user$

Any suggestions?