Allow all Python linter executables to be set to pipenv.

It appends ` run {linter_name}`, analogously to the Ruby linters when
the executable is set to `bundle`

test/command_callback/test_mypy_command_callback.vader

@@ -95,3 +95,12 @@ Execute(You should able able to use the global mypy instead):
   \   . ' --show-column-numbers  '
   \   . '--shadow-file %s %t %s',
   \ ale_linters#python#mypy#GetCommand(bufnr(''))
+
+Execute(Setting executable to 'pipenv' appends 'run mypy'):
+  let g:ale_python_mypy_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#path#BufferCdString(bufnr(''))
+  \   . ale#Escape('path/to/pipenv') . ' run mypy'
+  \   . ' --show-column-numbers  --shadow-file %s %t %s',
+  \ ale_linters#python#mypy#GetCommand(bufnr(''))

test/command_callback/test_prospector_command_callback.vader

@@ -0,0 +1,23 @@
+Before:
+  Save g:ale_python_mypy_executable
+  Save g:ale_python_mypy_options
+
+  unlet! g:ale_python_mypy_executable
+  unlet! g:ale_python_mypy_options
+
+  runtime ale_linters/python/prospector.vim
+
+After:
+  Restore
+
+  unlet! b:executable
+
+  call ale#linter#Reset()
+
+Execute(Setting executable to 'pipenv' appends 'run prospector'):
+  let g:ale_python_prospector_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#Escape('path/to/pipenv') . ' run prospector'
+  \   .  '  --messages-only --absolute-paths --zero-exit --output-format json %s',
+  \ ale_linters#python#prospector#GetCommand(bufnr(''))

test/command_callback/test_pycodestyle_command_callback.vader

@@ -25,3 +25,10 @@ Execute(The pycodestyle executable should be configurable):
 
   AssertEqual ale#Escape('~/.local/bin/pycodestyle') . '  -',
   \ ale_linters#python#pycodestyle#GetCommand(bufnr(''))
+
+Execute(Setting executable to 'pipenv' appends 'run pycodestyle'):
+  let g:ale_python_pycodestyle_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#Escape('path/to/pipenv') . ' run pycodestyle  -',
+  \ ale_linters#python#pycodestyle#GetCommand(bufnr(''))

test/command_callback/test_pyflakes_command_callback.vader

@@ -47,3 +47,10 @@ Execute(You should be able to override the pyflakes virtualenv lookup):
 
   AssertEqual ale#Escape('pyflakes') . ' %t',
   \ ale_linters#python#pyflakes#GetCommand(bufnr(''))
+
+Execute(Setting executable to 'pipenv' appends 'run pyflakes'):
+  let g:ale_python_pyflakes_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#Escape('path/to/pipenv') . ' run pyflakes %t',
+  \ ale_linters#python#pyflakes#GetCommand(bufnr(''))

test/command_callback/test_pylint_command_callback.vader

@@ -102,3 +102,12 @@ Execute(You should able able to use the global pylint instead):
   \ ale#path#BufferCdString(bufnr(''))
   \   . ale#Escape('pylint') . ' ' . b:command_tail,
   \ ale_linters#python#pylint#GetCommand(bufnr(''))
+
+Execute(Setting executable to 'pipenv' appends 'run pylint'):
+  let g:ale_python_pylint_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#path#BufferCdString(bufnr(''))
+  \   . ale#Escape('path/to/pipenv') . ' run pylint'
+  \   . '  --output-format text --msg-template="{path}:{line}:{column}: {msg_id} ({symbol}) {msg}" --reports n %s',
+  \ ale_linters#python#pylint#GetCommand(bufnr(''))

test/command_callback/test_pyls_command_callback.vader

@@ -47,3 +47,10 @@ Execute(You should be able to override the pyls virtualenv lookup):
 
   AssertEqual ale#Escape('pyls'),
   \ ale_linters#python#pyls#GetCommand(bufnr(''))
+
+Execute(Setting executable to 'pipenv' appends 'run pyls'):
+  let g:ale_python_pyls_executable = 'path/to/pipenv'
+
+  AssertEqual
+  \ ale#Escape('path/to/pipenv') . ' run pyls',
+  \ ale_linters#python#pyls#GetCommand(bufnr(''))