Redmine

I don't know what DB you use.
You need to remove mail column from users table by hand.
source:tags/3.0.3/db/migrate/20150113213922_remove_users_mail.rb#L3

We cannot do anything.
If you have backup and you can reproduce it, please report to Rails team.

Hi Toshi.
May be i was not clear. By executing the migration script that you mention breaks

1. We downloaded and installed the latest version from redmine
2. Restored backup from redmine 2
3. executed migrate
   1. note migrate deleted the user.mail column
4. tried to login got the error. if the migration script mentioned above will be skipped the upgraded installation will work

Started POST "/login" for 192.168.*.* at 2015-05-12 13:21:21 -0400
Processing by AccountController#login as HTML
  Parameters: {"utf8"=>"â", "authenticity_token"=>"qcgBEwRb1y6CXRs9L+D5ij+CroUOOHcaix+jwwcqa71PHEr3B8qpHJHgZ0cE8+4kcj13Hi091ZVuD6ViKzVv7A==", "back_url"=>"http://*.*.*.*/login", "username"=>"_user_", "password"=>"[FILTERED]", "login"=>"Login »"}
  Current user: anonymous
Successful authentication for '_user_' from 192.168.*.* at 2015-05-12 17:21:21 UTC
Redirected to http://*.*.*.*/my/page
Completed 302 Found in 19ms (ActiveRecord: 14.3ms)
Started GET "/my/page" for 192.168.*.* at 2015-05-12 13:21:21 -0400
Processing by MyController#page as HTML
  Current user: _user_ (id=37)
  Rendered issues/_list_simple.html.erb (7.1ms)
  Rendered my/blocks/_issuesassignedtome.html.erb (368.9ms)
Mysql2::Error: Unknown column 'users.mail' in 'field list': SELECT `issues`.`id` AS t0_r0, `issues`.`tracker_id` AS t0_r1, `issues`.`project_id` AS t0_r2, `issues`.`subject` AS t0_r3, `issues`.`description` AS t0_r4, `issues`.`due_date` AS t0_r5, `issues`.`category_id` A
S t0_r6, `issues`.`status_id` AS t0_r7, `issues`.`assigned_to_id` AS t0_r8, `issues`.`priority_id` AS t0_r9, `issues`.`fixed_version_id` AS t0_r10, `issues`.`author_id` AS t0_r11, `issues`.`lock_version` AS t0_r12, `issues`.`created_on` AS t0_r13, `issues`.`updated_on` A
S t0_r14, `issues`.`start_date` AS t0_r15, `issues`.`done_ratio` AS t0_r16, `issues`.`estimated_hours` AS t0_r17, `issues`.`parent_id` AS t0_r18, `issues`.`root_id` AS t0_r19, `issues`.`lft` AS t0_r20, `issues`.`rgt` AS t0_r21, `issues`.`is_private` AS t0_r22, `issues`.`
closed_on` AS t0_r23, `projects`.`id` AS t1_r0, `projects`.`name` AS t1_r1, `projects`.`description` AS t1_r2, `projects`.`homepage` AS t1_r3, `projects`.`is_public` AS t1_r4, `projects`.`parent_id` AS t1_r5, `projects`.`created_on` AS t1_r6, `projects`.`updated_on` AS t
1_r7, `projects`.`identifier` AS t1_r8, `projects`.`status` AS t1_r9, `projects`.`lft` AS t1_r10, `projects`.`rgt` AS t1_r11, `projects`.`inherit_members` AS t1_r12, `trackers`.`id` AS t2_r0, `trackers`.`name` AS t2_r1, `trackers`.`is_in_chlog` AS t2_r2, `trackers`.`posi
tion` AS t2_r3, `trackers`.`is_in_roadmap` AS t2_r4, `trackers`.`fields_bits` AS t2_r5, `trackers`.`default_status_id` AS t2_r6, `enumerations`.`id` AS t3_r0, `enumerations`.`name` AS t3_r1, `enumerations`.`position` AS t3_r2, `enumerations`.`is_default` AS t3_r3, `enume
rations`.`type` AS t3_r4, `enumerations`.`active` AS t3_r5, `enumerations`.`project_id` AS t3_r6, `enumerations`.`parent_id` AS t3_r7, `enumerations`.`position_name` AS t3_r8, `users`.`id` AS t4_r0, `users`.`login` AS t4_r1, `users`.`hashed_password` AS t4_r2, `users`.`f
irstname` AS t4_r3, `users`.`lastname` AS t4_r4, `users`.`mail` AS t4_r5, `users`.`admin` AS t4_r6, `users`.`status` AS t4_r7, `users`.`last_login_on` AS t4_r8, `users`.`language` AS t4_r9, `users`.`auth_source_id` AS t4_r10, `users`.`created_on` AS t4_r11, `users`.`upda
ted_on` AS t4_r12, `users`.`type` AS t4_r13, `users`.`identity_url` AS t4_r14, `users`.`mail_notification` AS t4_r15, `users`.`salt` AS t4_r16 FROM `issues` INNER JOIN `projects` ON `projects`.`id` = `issues`.`project_id` LEFT OUTER JOIN `trackers` ON `trackers`.`id` = `
issues`.`tracker_id` LEFT OUTER JOIN `enumerations` ON `enumerations`.`id` = `issues`.`priority_id` AND `enumerations`.`type` IN ('IssuePriority') LEFT OUTER JOIN `users` ON `users`.`id` = `issues`.`assigned_to_id` WHERE (((projects.status <> 9 AND projects.id IN (SELECT
 em.project_id FROM enabled_modules em WHERE em.name='issue_tracking')) AND ((projects.is_public = 1 AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (2,8,19,20,26) AND ((issues.is_private = 0 OR issues.
author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (2,8,20) AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (18,20,24,26) AND ((issues.is_private = 0 OR issues.author_id = 37
 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (20) AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72))))))) AND `issues`.`project_id` IN (8, 18, 20, 19, 26, 2, 24) AND ((start_date>='2015-05-10' and start_dat
e<='2015-05-16') or (due_date>='2015-05-10' and due_date<='2015-05-16'))
  Rendered my/blocks/_calendar.html.erb (11.2ms)
  Rendered my/page.html.erb within layouts/base (384.9ms)
Completed 500 Internal Server Error in 411ms (ActiveRecord: 37.8ms)

ActionView::Template::Error (Mysql2::Error: Unknown column 'users.mail' in 'field list': SELECT `issues`.`id` AS t0_r0, `issues`.`tracker_id` AS t0_r1, `issues`.`project_id` AS t0_r2, `issues`.`subject` AS t0_r3, `issues`.`description` AS t0_r4, `issues`.`due_date` AS t0
_r5, `issues`.`category_id` AS t0_r6, `issues`.`status_id` AS t0_r7, `issues`.`assigned_to_id` AS t0_r8, `issues`.`priority_id` AS t0_r9, `issues`.`fixed_version_id` AS t0_r10, `issues`.`author_id` AS t0_r11, `issues`.`lock_version` AS t0_r12, `issues`.`created_on` AS t0
_r13, `issues`.`updated_on` AS t0_r14, `issues`.`start_date` AS t0_r15, `issues`.`done_ratio` AS t0_r16, `issues`.`estimated_hours` AS t0_r17, `issues`.`parent_id` AS t0_r18, `issues`.`root_id` AS t0_r19, `issues`.`lft` AS t0_r20, `issues`.`rgt` AS t0_r21, `issues`.`is_p
rivate` AS t0_r22, `issues`.`closed_on` AS t0_r23, `projects`.`id` AS t1_r0, `projects`.`name` AS t1_r1, `projects`.`description` AS t1_r2, `projects`.`homepage` AS t1_r3, `projects`.`is_public` AS t1_r4, `projects`.`parent_id` AS t1_r5, `projects`.`created_on` AS t1_r6,
 `projects`.`updated_on` AS t1_r7, `projects`.`identifier` AS t1_r8, `projects`.`status` AS t1_r9, `projects`.`lft` AS t1_r10, `projects`.`rgt` AS t1_r11, `projects`.`inherit_members` AS t1_r12, `trackers`.`id` AS t2_r0, `trackers`.`name` AS t2_r1, `trackers`.`is_in_chlo
g` AS t2_r2, `trackers`.`position` AS t2_r3, `trackers`.`is_in_roadmap` AS t2_r4, `trackers`.`fields_bits` AS t2_r5, `trackers`.`default_status_id` AS t2_r6, `enumerations`.`id` AS t3_r0, `enumerations`.`name` AS t3_r1, `enumerations`.`position` AS t3_r2, `enumerations`.
`is_default` AS t3_r3, `enumerations`.`type` AS t3_r4, `enumerations`.`active` AS t3_r5, `enumerations`.`project_id` AS t3_r6, `enumerations`.`parent_id` AS t3_r7, `enumerations`.`position_name` AS t3_r8, `users`.`id` AS t4_r0, `users`.`login` AS t4_r1, `users`.`hashed_p
assword` AS t4_r2, `users`.`firstname` AS t4_r3, `users`.`lastname` AS t4_r4, `users`.`mail` AS t4_r5, `users`.`admin` AS t4_r6, `users`.`status` AS t4_r7, `users`.`last_login_on` AS t4_r8, `users`.`language` AS t4_r9, `users`.`auth_source_id` AS t4_r10, `users`.`created
_on` AS t4_r11, `users`.`updated_on` AS t4_r12, `users`.`type` AS t4_r13, `users`.`identity_url` AS t4_r14, `users`.`mail_notification` AS t4_r15, `users`.`salt` AS t4_r16 FROM `issues` INNER JOIN `projects` ON `projects`.`id` = `issues`.`project_id` LEFT OUTER JOIN `tra
ckers` ON `trackers`.`id` = `issues`.`tracker_id` LEFT OUTER JOIN `enumerations` ON `enumerations`.`id` = `issues`.`priority_id` AND `enumerations`.`type` IN ('IssuePriority') LEFT OUTER JOIN `users` ON `users`.`id` = `issues`.`assigned_to_id` WHERE (((projects.status <>
 9 AND projects.id IN (SELECT em.project_id FROM enabled_modules em WHERE em.name='issue_tracking')) AND ((projects.is_public = 1 AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (2,8,19,20,26) AND ((iss
ues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (2,8,20) AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (18,20,24,26) AND ((issues.is_private
 = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72)))) OR (projects.id IN (20) AND ((issues.is_private = 0 OR issues.author_id = 37 OR issues.assigned_to_id IN (37,34,35,72))))))) AND `issues`.`project_id` IN (8, 18, 20, 19, 26, 2, 24) AND ((start_dat
e>='2015-05-10' and start_date<='2015-05-16') or (due_date>='2015-05-10' and due_date<='2015-05-16'))):
    1: <h3><%= l(:label_calendar) %></h3>
    2:
    3: <% calendar = Redmine::Helpers::Calendar.new(Date.today, current_language, :week)
    4:    calendar.events = calendar_items(calendar.startdt, calendar.enddt) %>
    5:
    6: <%= render :partial => 'common/calendar', :locals => {:calendar => calendar } %>
  app/helpers/my_helper.rb:27:in `calendar_items'
  app/views/my/blocks/_calendar.html.erb:4:in `_app_views_my_blocks__calendar_html_erb___3760717535853276390_37816420'
  app/views/my/page.html.erb:11:in `block in _app_views_my_page_html_erb__3855367182213369000_70030794868640'
  app/views/my/page.html.erb:8:in `each'
  app/views/my/page.html.erb:8:in `_app_views_my_page_html_erb__3855367182213369000_70030794868640'

This error shows that you didn't properly stop and restart your Redmine server.
Keeping the users.mail column will trigger other errors now or in the future, please don't skip migrations. Just make sure that you restart your Redmine server.