Bug report

Bug summary
Processing default fmt='' named parameter, errorbar falls back to rcParams linestyle
If property cycle includes dotted or dashed lines they are ignored

Code for reproduction

import matplotlib.pyplot as plt
plt.rc("axes", prop_cycle = 'cycler(linestyle=["-","--",":"])'
plt.errorbar(x=[1,3,4],y=[1,2,3],yerr=0.5)
plt.errorbar(x=[1,3,4],y=[0,1,2],yerr=0.5)
plt.show()

Actual outcome
all lines are solid

Possible solution is to start with an empty dictionary if fmt parameter is an empty line
instead of lines 2880-2882 in axes/_axes.py put the following

        if fmt=='':
            fmt_style_kwargs={}
        else:
            fmt_style_kwargs = {k: v for k, v in
                            zip(('linestyle', 'marker', 'color'),
                                _process_plot_format(fmt)) if v is not None}

Because code queries the property cycle, I assume it was intended to pick up the values, not override them after processing an empty fmt line.
Matplotlib version

• Operating system: Windows 10
• Matplotlib version: 2.1.0
• Matplotlib backend (print(matplotlib.get_backend())): module://ipykernel.pylab.backend_inline
• Python version: 3.6.2
• Jupyter version (if applicable): 5.2.2
• Other libraries:

WinPython