Drop Python 2.6 support

[mayeut]

Summary

• OS: ALL
• Bug fix: no
• Type: core
• Fixes: Drop Python 2.6 support in unit tests and scripts, deprecate it in psutil #1053

Description

Let's drop python 2.6 support. It's not being tested anymore, its usage was mostly linked to CentOS 6 (c.f. #1053) which is now EOL. The stats for python 2.6 downloads also show that it's not being used anymore (0 downloads for 5.8.0 version, 67 downloads across all versions for the last month).

pypinfo -l 25 --percent --where 'file.version = "5.8.0" AND file.project = "psutil" AND details.installer.name = "pip"' psutil pyversion version  
Served from cache: False
Data processed: 1.47 GiB
Data billed: 1.47 GiB
Estimated cost: $0.01

| python_version | version | percent | download_count |
| -------------- | ------- | ------- | -------------- |
| 3.7            | 5.8.0   |  55.45% |     15,460,755 |
| 3.8            | 5.8.0   |  16.87% |      4,703,807 |
| 3.6            | 5.8.0   |  10.90% |      3,040,032 |
| 3.9            | 5.8.0   |   8.56% |      2,387,500 |
| 2.7            | 5.8.0   |   5.31% |      1,480,235 |
| 3.5            | 5.8.0   |   2.02% |        562,382 |
| 3.10           | 5.8.0   |   0.88% |        246,692 |
| 3.4            | 5.8.0   |   0.00% |          1,213 |
| 3.11           | 5.8.0   |   0.00% |            301 |
| 3.2            | 5.8.0   |   0.00% |              2 |
| Total          |         |         |     27,882,919 |

pypinfo --percent psutil pyversion
Served from cache: False
Data processed: 1.19 GiB
Data billed: 1.19 GiB
Estimated cost: $0.01

| python_version | percent | download_count |
| -------------- | ------- | -------------- |
| 3.7            |  52.29% |     16,852,218 |
| 3.8            |  16.73% |      5,391,531 |
| 3.6            |  12.94% |      4,170,766 |
| 2.7            |   7.77% |      2,504,686 |
| 3.9            |   7.59% |      2,447,477 |
| 3.5            |   1.85% |        596,800 |
| 3.10           |   0.80% |        258,639 |
| 3.4            |   0.02% |          5,583 |
| 3.11           |   0.00% |            304 |
| 2.6            |   0.00% |             67 |
| Total          |         |     32,228,071 |

[mayeut]

% pypinfo -l 25 --percent --where 'file.version = "5.9.0" AND file.project = "psutil" AND details.installer.name = "pip"' psutil pyversion version  

Served from cache: False
Data processed: 1.69 GiB
Data billed: 1.69 GiB
Estimated cost: $0.01

| python_version | version | percent | download_count |
| -------------- | ------- | ------- | -------------- |
| 3.7            | 5.9.0   |  47.84% |     14,417,950 |
| 3.8            | 5.9.0   |  29.57% |      8,910,583 |
| 3.9            | 5.9.0   |  10.42% |      3,138,894 |
| 3.6            | 5.9.0   |   7.03% |      2,119,229 |
| 3.10           | 5.9.0   |   2.65% |        797,396 |
| 2.7            | 5.9.0   |   2.29% |        691,481 |
| 3.5            | 5.9.0   |   0.19% |         56,675 |
| 3.11           | 5.9.0   |   0.01% |          1,806 |
| 3.4            | 5.9.0   |   0.00% |            691 |
| 3.3            | 5.9.0   |   0.00% |              1 |
| 3.2            | 5.9.0   |   0.00% |              1 |
| Total          |         |         |     30,134,707 |

% pypinfo -l 25 --percent psutil pyversion
Served from cache: False
Data processed: 1.36 GiB
Data billed: 1.36 GiB
Estimated cost: $0.01

| python_version | percent | download_count |
| -------------- | ------- | -------------- |
| 3.7            |  43.71% |     18,705,663 |
| 3.8            |  25.82% |     11,047,943 |
| 3.9            |  11.33% |      4,850,155 |
| 3.6            |  10.55% |      4,516,914 |
| 2.7            |   5.18% |      2,217,079 |
| 3.10           |   2.00% |        854,787 |
| 3.5            |   1.39% |        595,572 |
| 3.4            |   0.01% |          4,693 |
| 3.11           |   0.00% |          1,995 |
| 3.3            |   0.00% |             17 |
| 2.6            |   0.00% |              6 |
| 3.2            |   0.00% |              2 |
| None           |   0.00% |              1 |
| Total          |         |     42,794,827 |

[giampaolo]

Agreed. Let's kill it for good.