id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
309481761,MDU6SXNzdWUzMDk0ODE3NjE=,2024,multiple facetgrid.map calls screw up colorbar,2448579,closed,0,,,2,2018-03-28T18:34:02Z,2018-09-26T00:55:33Z,2018-09-26T00:55:33Z,MEMBER,,,,"#### Code Sample, a copy-pastable example if possible

This code 
```python
da = xr.DataArray(np.random.randn(10, 20, 8))

hdl = da.plot(col_wrap = 4, row='dim_2')
```

yields this image:
![image](https://user-images.githubusercontent.com/2448579/38048698-ea91b60e-327a-11e8-8e7b-8a7544b8d6c8.png)

Then, running this:
```
def mark_point(color='k'):
    plt.plot(10, 4, 'ko')

hdl.map(mark_point)
```

gives

![image](https://user-images.githubusercontent.com/2448579/38048731-0913dd32-327b-11e8-9b9d-be998e9448aa.png)

#### Problem description

Calling `facetgrid.map` calls `facetgrid._finalize_grid` which calls `tight_layout` which screws up the colorbar (eventually).

Quoting https://matplotlib.org/users/tight_layout_guide.html#colorbar
> If you create a colorbar with the colorbar() command, the created colorbar is an instance of Axes, not Subplot, so tight_layout does not work. With Matplotlib v1.1, you may create a colorbar as a subplot using the gridspec.

So the solution could involve writing a custom colorbar function.
#### Output of ``xr.show_versions()``

<details>
commit: None
python: 3.6.4.final.0
python-bits: 64
OS: Linux
OS-release: 4.13.0-36-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

xarray: 0.10.0+dev86.g9abf5ad
pandas: 0.22.0
numpy: 1.14.2
scipy: 1.0.0
netCDF4: 1.3.1
h5netcdf: 0.5.0
h5py: 2.7.1
Nio: None
zarr: 2.2.0
bottleneck: 1.2.1
cyordereddict: None
dask: 0.17.2
distributed: 1.21.4
matplotlib: 2.2.2
cartopy: 0.16.0
seaborn: 0.8.1
setuptools: 39.0.1
pip: 9.0.1
conda: 4.3.34
pytest: 3.4.2
IPython: 6.2.1
sphinx: 1.7.1
</details>
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/2024/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue